Topic Editors

School of Resources and Safety Engineering, Central South University, Changsha 410083, China
Hunan Provincial Key Laboratory of Safe Mining Techniques of Coal Mines, Hunan University of Science and Technology, Xiangtan 411201, China
School of Civil Engineering, Hefei University of Technology, Hefei 230009, China
School of Civil Engineering, Sun Yat-sen University, Zhuhai 519082, China
School of Resources and Safety Engineering, Central South University, Changsha 410083, China

New Trends in Rock Materials Mechanics and Engineering Geology

Abstract submission deadline
closed (20 March 2024)
Manuscript submission deadline
20 May 2024
Viewed by
74877

Topic Information

Dear Colleagues,

Rock mechanics is a complicated science compared with solid mechanics, fluid mechanics, and physics. The research object of rock mechanics is various types of rock mass engineering, whose rock mass material properties are affected by a series of defects (fissures, cracks, pores, voids, faults, etc.). The scale region of these defects is above the mesoscopic and microscopic scales, and below the macroscopic scale, where it is difficult to find statistical laws. Therefore, it is difficult to determine the reasonable statistical scale of volume units when constructing the theoretical system of mechanics.

As an independent applied basic discipline, rock mechanics has the following basic elements: independent research object, independent service field, independent testing machine and method, independent constitutive or physical law, and independent theoretical system. Research from the direction of these elements has guided the science and engineering technology of various rock mass problems in the past, and future advances will still revolve around them.

Hence, the aim of this Special Issue is to publish original research and review articles on new trends in these directions including test instruments and methods, mechanical properties of rock and rock mass, the theoretical analysis of mechanics, numerical simulation and intelligent algorithms, engineering rock mass techniques, and prediction and prevention techniques for rock mass disaster.

Prof. Dr. Hang Lin
Prof. Dr. Yanlin Zhao
Prof. Dr. YiXian Wang
Dr. Yu Chen
Dr. Rihong Cao
Topic Editors

Keywords

  • test instruments and methods
  • mechanical properties of rock and rock mass
  • theoretical analysis of mechanics
  • numerical simulation and intelligent algorithms
  • engineering rock mass techniques
  • prediction and prevention techniques for rock mass disaster

Participating Journals

Journal Name Impact Factor CiteScore Launched Year First Decision (median) APC
Applied Sciences
applsci
2.7 4.5 2011 16.9 Days CHF 2400 Submit
Minerals
minerals
2.5 3.9 2011 18.7 Days CHF 2400 Submit
Materials
materials
3.4 5.2 2008 13.9 Days CHF 2600 Submit
Energies
energies
3.2 5.5 2008 16.1 Days CHF 2600 Submit
Buildings
buildings
3.8 3.1 2011 14.6 Days CHF 2600 Submit

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Published Papers (48 papers)

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13 pages, 11755 KiB  
Article
The Difference in Shear Behavior and Strength between Loess and Paleosol and Their Prediction of Unsaturated Strength
by Pan Liu, Fuchu Dai, Zhiquan Huang and Jiaqi Wu
Appl. Sci. 2024, 14(8), 3301; https://doi.org/10.3390/app14083301 - 14 Apr 2024
Viewed by 193
Abstract
In recent decades, loess landslide events have attracted increasing attention in the South Jingyang tableland. To elucidate the mechanical mechanism of landslide initiation in the region, this work collected undisturbed loess and paleosol samples taking from the Q2 strata in the South [...] Read more.
In recent decades, loess landslide events have attracted increasing attention in the South Jingyang tableland. To elucidate the mechanical mechanism of landslide initiation in the region, this work collected undisturbed loess and paleosol samples taking from the Q2 strata in the South Jingyang tableland. A range of direct shear tests were carried out to explore the strength evolution law of shear zone soil subjected to a varying initial moisture content. In addition, soil water characteristic curves (SWCCs) were also charted and used for predicting the unsaturated shear strength. The findings show that the basic physical properties of the paleosol are different from those of loess due to their different pedogenic environments. The normal stress level and initial moisture content jointly determine whether the shear behavior is strain hardening or strain softening. The shear strength and strength parameters evidently diminish with an increasing initial moisture content, and cohesion contributes to the vast majority of strength attenuation. Paleosol samples possess higher values in shear strength and strength parameters than loess samples due to their stronger inter-particle cementation. The predictive formulas of unsaturated shear strength for undisturbed loess and paleosol are proposed, respectively, based on the Vanapalli model, and the calculated values of the strength prediction model are in perfect agreement with the experimental values. Full article
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16 pages, 2545 KiB  
Article
Spatial Variations of Deformation along a Strike-Slip Fault: A Case Study of Xianshuihe Fault Zone, Southwest China
by Jinxuan Li, Songfeng Guo, Shengwen Qi, Qianhui Wei, Bowen Zheng, Yu Zou, Yongchao Li, Yaguo Zhang and Xiao Lu
Appl. Sci. 2024, 14(6), 2439; https://doi.org/10.3390/app14062439 - 14 Mar 2024
Viewed by 492
Abstract
The distribution of damage zones around a fault has long been regarded as a frontier and hot spot in the field of geoscience but is still not fully understood. In this study, we conducted field investigations and tests around the Xianshuihe fault zone [...] Read more.
The distribution of damage zones around a fault has long been regarded as a frontier and hot spot in the field of geoscience but is still not fully understood. In this study, we conducted field investigations and tests around the Xianshuihe fault zone (XSHF), a left-lateral strike-slip fault with a length of about 400 km located in the eastern margin of the Tibetan Plateau. The results reveal that the fracture frequency and rock strength parameters present a spatially asymmetric distribution along the fault and have a negative power-law correlation with the distance from the fault. The widths of the damage zones are approximately 20.8 km and 17.1 km in the southwest and northeast directions, respectively. Combined with the previous studies, we presented a negative power-law function to depict the correlation between slip displacement and the width of the damage zone and found that the growth rate of damage zone in faults with low displacement is greater than that in those with large displacement. The study demonstrates that the asymmetric distribution of the damage zone surrounding the XSHF is mainly due to the stress redistribution in different damage zones stemming from the left echelon and different activity rates of the blocks on both sides of the XSHF. Full article
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20 pages, 4519 KiB  
Article
Shaft Wall Damage to High-Depth Inclined Ore Passes under Impact Wear Behavior
by Lichun Jiang, Haoyu Ji and Luanluan Xue
Appl. Sci. 2023, 13(24), 13065; https://doi.org/10.3390/app132413065 - 07 Dec 2023
Viewed by 624
Abstract
In order to study shaft wall damage resulting from ore drawing in ore passes, a theoretical model for predicting the shaft wall damage to high-depth inclined ore passes is constructed based on field surveys of 25 ore passes in a deep mine in [...] Read more.
In order to study shaft wall damage resulting from ore drawing in ore passes, a theoretical model for predicting the shaft wall damage to high-depth inclined ore passes is constructed based on field surveys of 25 ore passes in a deep mine in Yunnan, China. The mathematical expression of the total shaft wall damage volume is derived using the contact mechanics theory. Considering the structural characteristics of ore passes, and taking No. 1, 2, 3, and 9 ore passes as examples, combined with numerical simulation and an engineering case, the rationality of the proposed theoretical model is verified with respect to the initial collision position and the damage conditions of the shaft wall. The influence of, and sensitivity to, the ore block size P and the structural parameters of high-depth inclined ore passes on the total shaft wall damage volume Qtol are quantitatively analyzed. The results show that the calculation results of the theoretical model and numerical simulation are in good agreement with the actual engineering situations. Moreover, the ore-pass dip angle θ and the inclined angle of the chute α have a significant impact on the damage to the shaft wall, while the effects of the ore-pass depth H and the shaft diameter D are comparatively minor. With an increase in θ or α, Qtol generally first increases and then decreases. Qtol increases exponentially with P and increases steadily with D. H affects Qtol by influencing the collision frequency between the ore and the shaft wall. Therefore, in the mining design of deep mines, θ and α should be minimized as much as possible or adjusted to approach 90°, thereby reducing damage to the shaft wall. Secondly, ore block size should be strictly controlled to prevent collapses in the shaft wall caused by large ore blocks. This work provides technical support for the long-term safe operation of high-depth inclined ore passes. Full article
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17 pages, 4732 KiB  
Article
A Numerical Study of the Dynamic Crack Behavior of Brittle Material Induced by Blast Waves
by Haijun Yu, Ming Zou, Jinshan Sun, Yuntao Wang and Meng Wang
Materials 2023, 16(22), 7142; https://doi.org/10.3390/ma16227142 - 13 Nov 2023
Viewed by 636
Abstract
Blast stress waves profoundly impact engineering structures, exciting and affecting the rupture process in brittle construction materials. A novel numerical model was introduced to investigate the initiation and propagation of cracks subjected to blast stress waves within the borehole-crack configuration. Twelve models were [...] Read more.
Blast stress waves profoundly impact engineering structures, exciting and affecting the rupture process in brittle construction materials. A novel numerical model was introduced to investigate the initiation and propagation of cracks subjected to blast stress waves within the borehole-crack configuration. Twelve models were established with different crack lengths to simulate sandstone samples. The influence of crack length on crack initiation and propagation was investigated using those models. The linear equation of state was used to express the relationship between the pressure and density of the material. The major principal stress failure criterion was used to evaluate the failure of elements. A triangular pressure curve was adopted to produce the blast stress wave. The results indicated that the pre-crack length critically influenced the crack initiation and propagation mechanism by analyzing the stress history at the crack tip, crack propagation velocity, and distance. The inducement of a P-wave and S-wave is paramount in models with a short pre-crack. For long pre-crack models, Rayleigh waves significantly contribute to crack propagation. Full article
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15 pages, 8626 KiB  
Article
The Influence of Different Shear Directions on the Shear Resistance Characteristics of Rock Joints
by Xipeng Lai, Wei Yuan, Wei Wang, Ruifeng Sun, Pengzhao Du, Hang Lin, Xiaodong Fu, Qinghe Niu and Chao Yin
Buildings 2023, 13(10), 2556; https://doi.org/10.3390/buildings13102556 - 10 Oct 2023
Viewed by 634
Abstract
The joint roughness coefficient JRC of rock joints is an important parameter for measuring the geometric morphology of rock joints. However, the parameter obtained from traditional calculation methods has certain limitations in reflecting the differences in shear strength of rock joints in different [...] Read more.
The joint roughness coefficient JRC of rock joints is an important parameter for measuring the geometric morphology of rock joints. However, the parameter obtained from traditional calculation methods has certain limitations in reflecting the differences in shear strength of rock joints in different shear directions with the same orientation. Firstly, native joint surface test blocks were cast using three-dimensional reverse reconstruction technology. Subsequently, direct shear tests were conducted under different normal stress and shear direction conditions, followed by numerical simulations using the finite difference software Flac3d. The JRC coefficient calculation method proposed by Yuan was modified and extended by considering the percentage of climbing sections and the effective contact area during the ramping process. This study indicates that the numerical simulation results are in good agreement with the shear test results. The introduction of the shear climbing rate SCR and the curvature coefficient of profile CCP is used to reflect the geometric differences of the joint surfaces in different shear directions. These two parameters are nonlinearly fitted with the experimental results, leading to a calculation formula that characterizes the shear strength characteristics of the joint surfaces in different shear directions. This novel formula is an extension of the JRC–JCS model. Full article
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15 pages, 11185 KiB  
Article
Simulation Study on Fire Product Movement Law and Evacuation in a University High-Rise Teaching Building
by Yan Cui, Hao Wang, Bo You, Chuan Cheng and Ming Li
Appl. Sci. 2023, 13(18), 10532; https://doi.org/10.3390/app131810532 - 21 Sep 2023
Cited by 2 | Viewed by 775
Abstract
High-rise teaching buildings are complex public buildings that combine the evacuation risks of school buildings and high-rise buildings. In this regard, studying fire product transport patterns and personnel evacuation characteristics of high-rise school buildings is crucial for safe and rapid evacuation. In this [...] Read more.
High-rise teaching buildings are complex public buildings that combine the evacuation risks of school buildings and high-rise buildings. In this regard, studying fire product transport patterns and personnel evacuation characteristics of high-rise school buildings is crucial for safe and rapid evacuation. In this paper, we applied Pyrosim2018 software to build a model of a teaching building and performed numerical fire simulation to analyze temperature, CO gas, and visibility to determine the available evacuation time ASET; meanwhile, we performed evacuation simulation by Pathfinder 2019 to determine the required evacuation time and analyze the congestion problem during evacuation. By improving the evacuation route, secondary simulations were conducted and compared with the previous results. The results show that visibility is the main factor affecting evacuation in of the event of a fire in this school building. Based on the visibility analysis, it is recommended that personnel evacuate from floors four and above within 709.2 S when the fire location is at a specific position on the third floor. While the original safety exits of the school building can avoid a large number of casualties, they cannot guarantee the safe evacuation of all people, and planning a reasonable evacuation route can obviously relieve the evacuation pressure in the high-rise corridor. Full article
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12 pages, 3586 KiB  
Article
Study on the Particle Surface Fractal Characteristics of Sulfide Ores
by Yan Cui, Jimeng Wang, Chuan Cheng, Bo You, Yong Liu and Ming Li
Appl. Sci. 2023, 13(16), 9199; https://doi.org/10.3390/app13169199 - 12 Aug 2023
Viewed by 913
Abstract
The fractal dimension is widely used in many fields as a parameter to characterize the geometric complexity and geometric distribution relationship of research objects. To study the surface characteristics of sulfide ore particles, the fractal theory was applied to quantitatively characterize the surface [...] Read more.
The fractal dimension is widely used in many fields as a parameter to characterize the geometric complexity and geometric distribution relationship of research objects. To study the surface characteristics of sulfide ore particles, the fractal theory was applied to quantitatively characterize the surface fractal dimension Ds of sulfide ore microparticles in three particle size ranges, 60–100 mesh, 100–140 mesh and >200 mesh, based on the area–perimeter method. Using an optical microscope, grain projection images of the particles were obtained. The grain shape and characteristics of sulfide ore particles were studied by means of an image processing system. The results demonstrate that the grain shape of sulfide ore particles can be expressed by fractal dimension, and the particle surface fractal dimension ranges from 2.4392 to 2.5492. It was found that the fractal properties begin to decrease due to the increasing of the particle size. The larger the fractal dimension, the finer the particles are. The fractal dimension of sulfide ore particles can be used as an important indicator of their particle shape distribution characteristics, which can provide important information for further study of the relevant physical and chemical properties of sulfide ore particles and provide a new theoretical method and basis for the adhesion and removal of sulfide ore dust. With the quantitative description of the fractal distribution of sulfide ore particles, a new way to study the adhesive force between particles is offered for further research. Full article
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23 pages, 7743 KiB  
Article
Investigation on the Stress and Deformation Evolution Laws of Shield Tunnelling through a Mining Tunnel Structure
by Entong Du, Lei Zhou and Ruizhen Fei
Appl. Sci. 2023, 13(14), 8489; https://doi.org/10.3390/app13148489 - 22 Jul 2023
Viewed by 946
Abstract
In the construction of a shield crossing an existing mined tunnel without load, it is imperative to develop corresponding design standards that reflect actual engineering force characteristics to ensure the successful completion of the tunnel construction. This study uses the MIDAS-GTS NX 2022 [...] Read more.
In the construction of a shield crossing an existing mined tunnel without load, it is imperative to develop corresponding design standards that reflect actual engineering force characteristics to ensure the successful completion of the tunnel construction. This study uses the MIDAS-GTS NX 2022 finite element software to facilitate the creation of a numerical model of a shield structure for an air-push-over mine tunnel project in Changsha, China while investigating the stress field’s evolution during shield construction and calculating the maximum positive and negative bending moments and maximum axial forces for different structures and other force states under various construction conditions. This study’s findings informed the design and construction optimisation of a shield tunnelling empty-push method. The outcomes of this numerical simulation led to several key findings: (1) The soil density exerted a significantly greater impact on the internal forces of the initial support structure than both the tunnel depth and soil Poisson’s ratio. Additionally, a sudden shift in internal forces occurred within the 300–350 mm range when the lining thickness was altered. (2) Factors such as the tunnel depth, soil density, soil Poisson’s ratio μ, and lining thickness similarly influenced the internal forces of the segment and the initial support. Notably, the backfill layer thickness significantly affected the segment’s maximum axial force, causing an abrupt change of approximately 300 mm. (3) It is essential to control the guide rail’s thickness under the shield machine equipment’s weight constraint to prevent it from becoming overly large. Full article
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17 pages, 8897 KiB  
Article
A DEM Study on Bearing Behavior of Floating Geosynthetic-Encased Stone Column in Deep Soft Clays
by Feng Liu, Panpan Guo, Xunjian Hu, Baojian Li, Haibo Hu and Xiaonan Gong
Appl. Sci. 2023, 13(11), 6838; https://doi.org/10.3390/app13116838 - 05 Jun 2023
Viewed by 852
Abstract
The use of geosynthetic-encased stone columns has been proven to be an economical and effective method for soft soil foundation treatment. This method is widely used in civil engineering projects at home and abroad. When the geosynthetic-encased stone columns are applied to deep [...] Read more.
The use of geosynthetic-encased stone columns has been proven to be an economical and effective method for soft soil foundation treatment. This method is widely used in civil engineering projects at home and abroad. When the geosynthetic-encased stone columns are applied to deep soft clays, they are in a floating state. The load-bearing deformation mechanism of geosynthetic-encased stone columns has changed. The interaction between the aggregates, geogrid, and soil is worth studying, especially at the bottom of the column. In this paper, the discrete element method is used to simulate a floating geosynthetic-encased stone column with a 280 mm encasement depth in deep soft clays. The load-bearing deformation characteristics and mesoscopic mechanism of the floating geosynthetic-encased stone column are studied. The results show that there are large vertical and radial stresses in the top region. Moreover, the porosity and sliding fraction of aggregates in this region increase with settlement, and the coordination number decreases with settlement. The vertical and radial stresses of the soil near the column body are not affected much by the column body. When the encasement depth exceeds 280 mm, the bearing capacity of the FGESC does not increase much. The encasement depth controls the failure mode of the floating geosynthetic-encased stone column. As the encasement depth increases, the failure mode of the floating geosynthetic-encased stone column gradually transitions from swelling deformation to penetration failure. Full article
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11 pages, 3092 KiB  
Article
A Mathematical Model for Predicting the Droplet Size of Micro-Fog Nozzle with Circular-Hole Rotating Core Based on Orthogonal Design
by Yan Cui, Chuan Cheng, Pengfei Wang, Yong Liu, Runqiu Li, Yong Zhang, Ming Li and Shilin Li
Appl. Sci. 2023, 13(11), 6670; https://doi.org/10.3390/app13116670 - 30 May 2023
Viewed by 855
Abstract
The circular-hole rotating core fog nozzle has excellent atomization performance and has been widely used in the realm of spray dust. As part of this study, a mathematical model was developed for predicting the Sauter mean diameter (SMD) of nozzles of this type. [...] Read more.
The circular-hole rotating core fog nozzle has excellent atomization performance and has been widely used in the realm of spray dust. As part of this study, a mathematical model was developed for predicting the Sauter mean diameter (SMD) of nozzles of this type. The coaction between the SMD of the nozzle and the three influencing factors of axial distance, water supply pressure, and outlet diameter was investigated based on the customized spray’s experimental platform and orthogonal design method. According to the comparative analysis of the size range, the axial distance, outlet diameter and water supply pressure are three parameters that affect the SMD of the nozzle, and the degree of influence is axial distance > outlet diameter > water supply pressure. On this basis, a mathematical model was developed using the multiple regression method to predict the SMD of the nozzle. We analyzed the results and compared them to the SMD value predicted by the multiple regression mathematical model and the orthogonal experiment results. The change trend was the same, the values were essentially the same, and the average relative error was just 16.11%. Accordingly, the mathematical model presented in this paper may be used for the prediction and calculation of the droplet size for circular-hole rotating core micro-fog nozzles. Full article
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17 pages, 5306 KiB  
Article
Digital Rock Analysis on the Influence of Coarse Micro-Fractures on Petrophysical Properties in Tight Sandstone Reservoirs
by Lei Liu, Jun Yao, Hai Sun, Lei Zhang and Kai Zhang
Appl. Sci. 2023, 13(9), 5237; https://doi.org/10.3390/app13095237 - 22 Apr 2023
Cited by 2 | Viewed by 1208
Abstract
Tight sandstone reservoirs, as typical unconventional reservoirs, have attracted more and more attention worldwide. Compared to conventional reservoirs, the complex microscopic pore structures and micro-fractures of the tight reservoirs are developed, and fluid flow in the tight sandstone reservoir is very complicated. Therefore, [...] Read more.
Tight sandstone reservoirs, as typical unconventional reservoirs, have attracted more and more attention worldwide. Compared to conventional reservoirs, the complex microscopic pore structures and micro-fractures of the tight reservoirs are developed, and fluid flow in the tight sandstone reservoir is very complicated. Therefore, studying the influence of fractures on the rock topological structure and the flow characteristics between micro-fractures and the matrix is critical to the development of tight sandstone reservoirs. In light of the intricate nature of micro-fractures, digital rock analysis technology is utilized to address this issue instead of traditional experimental methods. Firstly, the selected tight rock is scanned by X-ray computed tomography (XCT), and then the natural tight digital rock is reconstructed by filtering and binary segmentation. Secondly, micro-fracture with different shapes is added to the digital rock. Then, a pore network model extracted by the maximum ball method is adopted to conduct the flow simulation. The study finds that the distribution of pore throat radius changes with increasing fracture aperture and length and that the permeability and capillary pressure curves are influenced by fracture aperture and length in the direction of connectivity. The impact of micro-fracture dip angle on pore throat structure is significant with changes in permeability and fluid flow in different directions. Overall, the study emphasizes the importance of fracture aperture and length in determining the properties and behavior of tight sandstone reservoirs and highlights the usefulness of digital rock analysis technology in providing insights into complex microstructures. Full article
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27 pages, 14410 KiB  
Article
A Theory of Slope Shear Scouring and the Failure Mechanism of PFC3D on a Gangue Slope
by Yun Tian, Yong Wu, Hao Wang, Hongtao Li, Lindong He and Hong Zhao
Appl. Sci. 2023, 13(8), 5066; https://doi.org/10.3390/app13085066 - 18 Apr 2023
Viewed by 1311
Abstract
In this paper, scouring shear failure theory is optimized based on the gangue slope near the thermal power field in Baiguo Town, Panzhou City, Guizhou Province. Based on the particle flow PFC (particle flow code) 3D fluid–solid coupling method, the scouring failure mechanism [...] Read more.
In this paper, scouring shear failure theory is optimized based on the gangue slope near the thermal power field in Baiguo Town, Panzhou City, Guizhou Province. Based on the particle flow PFC (particle flow code) 3D fluid–solid coupling method, the scouring failure mechanism of ditch no. 5 of the gangue slope is comprehensively analyzed from the perspectives of the failure mode, displacement, motion track, and stress–strain. We consider the scouring shear theory in respect of (c, φ); this theory is dominated by two types of scouring intensity factors and can effectively explain the internal mechanisms of gully formation. The rainfall scouring failure of gangue slopes can be divided into four stages: (1) integral splash erosion and local pitting at the bottom of the slope; (2) erosion diversion and pitting in the slope; (3) the tributary–slope crest extension schist erosion stage; and (4) integral gully erosion and the landslide stage. The failure process is not only characterized by discontinuous failure but also occurs in the order of bottom–middle–branch–top. A three-section stepped effect is observed during the process in which the gangue is scoured and destroyed, which fully verifies the intermittent characteristics of the scouring and destruction of gangue slopes. During the whole process, the maximum displacement is concentrated at the top of the slope, and its proportions are as follows: top of the slope > tributary > middle of the slope > foot of the slope. The peak displacement of the slope crest in the horizontal Y-direction accounts for 41.76%, and that in the Z-direction accounts for 45.84%. Scouring deposits can be divided into the arc erosion deposit mode and the sector erosion deposit mode. Mainstream gullies primarily control whether deposits are characterized as arc or straight erosion deposits. The later stage of the second phase of scouring is the incubation period of the tributary gully. The large accumulation makes the stress at the bottom of the slope increase sharply, and the fluctuation value is between 2 and 6.8 MPa. The generation of the branch notch is mainly determined by X-direction stress, and 8.6 MPa is the critical stress. In efforts to prevent and control rainfall and landslide, the slope foot area should be preferentially protected, and the soil mass in the slope should be reduced to prevent the maximum energy fluctuation caused by scouring, so as to prevent significant displacement damage of the slope top. Full article
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20 pages, 5806 KiB  
Review
A Review of Mechanical Properties and Rockburst Investigation of Transversely Isotropic Rocks by Experimental Technique
by Xuefeng Si, Song Luo and Yong Luo
Materials 2023, 16(8), 3183; https://doi.org/10.3390/ma16083183 - 18 Apr 2023
Cited by 14 | Viewed by 1917
Abstract
Under complex geostress caused by long-term geological evolution, approximately parallel bedding structures are normally created in rocks due to sedimentation or metamorphism. This type of rock is known as transversely isotropic rock (TIR). Due to the existence of bedding planes, the mechanical properties [...] Read more.
Under complex geostress caused by long-term geological evolution, approximately parallel bedding structures are normally created in rocks due to sedimentation or metamorphism. This type of rock is known as transversely isotropic rock (TIR). Due to the existence of bedding planes, the mechanical properties of TIR are quite different from those of relatively homogeneous rocks. The purpose of this review is to discuss the research progress into the mechanical properties and failure characteristics of TIR and to explore the influence of the bedding structure on the rockburst characteristics of the surrounding rocks. First, the P-wave velocity characteristics of the TIR is summarized, followed by the mechanical properties (e.g., the uniaxial compressive strength, the triaxial compressive strength, and tensile strength) and the related failure characteristics of the TIR. The strength criteria of the TIR under triaxial compression are also summarized in this section. Second, the research progress of the rockburst tests on the TIR is reviewed. Finally, six prospects for the study of the transversely isotropic rock are presented: (1) measuring the Brazilian tensile strength of the TIR; (2) establishing the strength criteria for the TIR; (3) revealing the influence mechanism of the mineral particles between the bedding planes on rock failure from the microscopic point of view; (4) investigating the mechanical properties of the TIR in complex environments; (5) experimentally investigating the rockburst of the TIR under the stress path of “the three-dimensional high stress + internal unloading + dynamic disturbance”; and (6) studying the influence of the bedding angle, thickness, and number on the rockburst proneness of the TIR. Finally, some conclusions are summarized. Full article
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17 pages, 2685 KiB  
Article
Study on the Damage Model of Non-Persistent Jointed Rock Mass under the Coupling of Freeze–Thaw and Shear
by Daxing Lei, Haixiang Hu, Yifan Chen, Hang Lin, Chaomei Zhang, Guangli Wang, Zhigang Lu and Yaoping Zhang
Materials 2023, 16(8), 3041; https://doi.org/10.3390/ma16083041 - 12 Apr 2023
Viewed by 1062
Abstract
Considering that a jointed rock mass in a cold area is often affected by periodic freeze–thaw cycles and shear failure, definitions for the mesoscopic and macroscopic damage to a jointed rock mass under the coupling of freeze–thaw and shear are proposed, and the [...] Read more.
Considering that a jointed rock mass in a cold area is often affected by periodic freeze–thaw cycles and shear failure, definitions for the mesoscopic and macroscopic damage to a jointed rock mass under the coupling of freeze–thaw and shear are proposed, and the damage mechanism is verified according to experimental results. The results show that: (1) the jointed rock specimens increase macro-joints and meso-defects, the mechanical properties deteriorate significantly under freeze–thaw cycles, and the damage degree becomes more and more significant with the increases in freeze–thaw cycles and joint persistency. (2) When the number of freeze–thaw cycles is constant, the total damage variable value gradually increases with the increase in joint persistency. The damage variable difference in specimens with different persistency is distinct, which is gradually reduced in the later cycles, indicating a weakening influence of persistency on the total damage variable. (3) The shear resistance of non-persistent jointed rock mass in a cold area is determined by the coupling effect of meso-damage and frost heaving macro-damage. The coupling damage variable can accurately describe the damage variation law of jointed rock mass under freeze–thaw cycles and shear load. Full article
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15 pages, 3632 KiB  
Article
Mechanical Characteristics of an Open-Buried Double-Arch Tunnel during Construction
by Yu-Liang Lin, Ya-Lin Guo, Guo-Lin Yang and Pei-Ran Zhang
Appl. Sci. 2023, 13(6), 3891; https://doi.org/10.3390/app13063891 - 18 Mar 2023
Viewed by 1430
Abstract
The open excavation and concealed construction method is widely adopted for the construction of bias double-arch tunnels. However, the mechanical behavior of the tunnel during the whole construction period by using the open excavation and concealed construction method is not well understood, and [...] Read more.
The open excavation and concealed construction method is widely adopted for the construction of bias double-arch tunnels. However, the mechanical behavior of the tunnel during the whole construction period by using the open excavation and concealed construction method is not well understood, and the basis for construction organization and optimization is lacking. Based on an open-buried double-arch tunnel on Xiajuan Road, Changsha City, China, on-site monitoring was carried out in terms of the deformation of the steel arch in the primary lining, the stress of reinforcement in the secondary lining, and the deformation of the surrounding rock during the construction process. The correlation between the vault settlement rate and the steel arch strain was analyzed. The results show that the maximum vault settlement and settling rate of the left and right caverns occur at different locations due to different supporting conditions. The peripheral displacement experiences a process of convergence inward and extension outward. The compressive steel stress in the secondary lining of the right cavern is greater than that in the left cavern, except for the points at the arch waist. The backfill above the left cavern reduces the loading on the lining of the right cavern, but it increases the loading on the left cavern. The bias effect of the open-buried double-arch tunnel is well controlled and balanced when the open excavation and concealed construction method is adopted. Full article
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22 pages, 10888 KiB  
Article
Study on Staged Damage Behaviors of Rock-like Materials with Different Brittleness Degrees Based on Multiple Parameters
by Tong Jiang, Li Wan, Wenxue Wang, Chao Xu, Chen Liu, Fanke Meng, Yuan Cui and Longfei Li
Materials 2023, 16(6), 2334; https://doi.org/10.3390/ma16062334 - 14 Mar 2023
Cited by 2 | Viewed by 1124
Abstract
Understanding the brittle fracture behavior of rock is crucial for engineering and Earth science. In this paper, based on acoustic emission (AE) and laser Doppler vibration (LDV) monitoring technology, the staged damage behaviors of rock-like materials with different brittleness degrees under uniaxial compression [...] Read more.
Understanding the brittle fracture behavior of rock is crucial for engineering and Earth science. In this paper, based on acoustic emission (AE) and laser Doppler vibration (LDV) monitoring technology, the staged damage behaviors of rock-like materials with different brittleness degrees under uniaxial compression are studied via multiple parameters. The results show that the brittleness degree determines the fracture mode. As the specimen’s brittleness degree increases, the tensile failure increases and shear failure decreases. AE activity is enhanced at the crack damage point. With an increasing specimen brittleness degree, different instability precursor information is shown during the unstable crack growth stage: the AE b value changes from the fluctuating to continuously decreasing state, and the natural frequency changes from the stable fluctuation to upward fluctuation state. The AE b value near the stress drop is the smallest, and it decreases with an increasing brittleness degree. The natural frequency reduction indicates the rock-like fracture. The natural frequency is a symbolic index that reflects staged damage characteristics and predicts the amount of energy released by brittle failure. These findings provide guidelines for rock stability monitoring and provide support for better responses to stability evaluations of rock slopes, rock collapses, and tunnel surrounding rock in engineering. Full article
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20 pages, 36520 KiB  
Article
An Innovative Method to Analyze the Hydraulic Fracture Reopening Pressure of Hot Dry Rock
by Deng-Deng Zhuang, Tu-Bing Yin, Zong-Xian Zhang, Adeyemi Aladejare, You Wu and Yang Qiao
Materials 2023, 16(3), 1118; https://doi.org/10.3390/ma16031118 - 28 Jan 2023
Viewed by 1379
Abstract
This paper focuses on a new test method and theoretical model for measuring and evaluating the reopening pressure during hot dry rock hydraulic fracturing. Firstly, rock blocks of four lithologies were collected from the hot dry rock strata. Hydraulic fracturing tests at high [...] Read more.
This paper focuses on a new test method and theoretical model for measuring and evaluating the reopening pressure during hot dry rock hydraulic fracturing. Firstly, rock blocks of four lithologies were collected from the hot dry rock strata. Hydraulic fracturing tests at high temperatures in real-time were conducted using drilled cubic specimens and drilled cubic specimens with a pre-crack. Breakdown pressure, reopening pressure, and fracture toughness were measured, respectively. In addition, Brazilian splitting tests at high temperatures in real-time were performed using Brazilian disc specimens to measure tensile strength. Secondly, an empirical equation for evaluating the reopening pressure during hot dry rock secondary fracturing was developed based on fracture mechanics and hydraulic fracturing theory. Third, the values calculated by the new equation, considering breakdown pressure, fracture toughness, and tensile strength, were compared to the values determined by the classical equation and to measurement results. It was found that the new equation predicted closer reopening pressure to the measurement results, regardless of the lithology of the hot dry rock. Moreover, with increasing temperature in the specimens, the error between the value calculated by the new equation and the measurement value remained low. In contrast, the difference between the classical equation predictions and the measurement results was widened. In addition, the reopening pressure was positively correlated with tensile strength and fracture toughness. Variations in lithology and temperature affected tensile strength and fracture toughness, which then changed the hot dry rock reopening pressure. Full article
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11 pages, 5642 KiB  
Article
An Experimental Study of the Relation between Mode I Fracture Toughness, KIc, and Critical Energy Release Rate, GIc
by Yang Qiao, Zong-Xian Zhang and Sheng Zhang
Materials 2023, 16(3), 1056; https://doi.org/10.3390/ma16031056 - 25 Jan 2023
Cited by 2 | Viewed by 1910
Abstract
The construction of the relation between the critical energy release rate, GIc, and the mode I fracture toughness, KIc, is of great significance for understanding the fracture mechanism and facilitating its application in engineering. In this study, [...] Read more.
The construction of the relation between the critical energy release rate, GIc, and the mode I fracture toughness, KIc, is of great significance for understanding the fracture mechanism and facilitating its application in engineering. In this study, fracture experiments using NSCB and CCCD specimens were conducted. The effects of specimen sizes, loading rate and lithology on the relation between GIc and KIc were studied. GIc was calculated by integrating the load–displacement curve according to Irwin’s approach. Based on the measured KIc and GIc of the rock specimens, a relation between GIc and KIc was found to be different from the classical formula under linear elasticity. It was found that both specimen size and loading rate do not influence this relation. Full article
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17 pages, 20584 KiB  
Article
Energy Evolution and Damage Characteristics of Rock Materials under Different Cyclic Loading and Unloading Paths
by Bing Sun, Haowei Yang, Junwei Fan, Xiling Liu and Sheng Zeng
Buildings 2023, 13(1), 238; https://doi.org/10.3390/buildings13010238 - 14 Jan 2023
Cited by 3 | Viewed by 1779
Abstract
In order to study the deformation and failure characteristics of rocks under different cyclic loading and unloading paths, three stress path tests were conducted, and acoustic emission (AE) monitoring was conducted simultaneously. The mechanical characteristics and AE characteristics under different stress paths were [...] Read more.
In order to study the deformation and failure characteristics of rocks under different cyclic loading and unloading paths, three stress path tests were conducted, and acoustic emission (AE) monitoring was conducted simultaneously. The mechanical characteristics and AE characteristics under different stress paths were analyzed, and the influences of the different stress paths on the energy dissipation and deformation damage were investigated. The law of energy evolution considering viscoelasticity under different stress paths was obtained. The concept of ultimate damage energy and its calculation method was proposed. The results show that the “hardening effect” of sandstone and granite under the constant lower limit (CLLCL) is the most significant in maximizing the mechanical property. The CLLCL imparts a stronger elastic property to rocks than the variable lower limit (VLLCL) does, while the VLLCL causes more damage to rocks than the CLLCL. A significant linear relationship between the proportion of damage energy and the proportion of elastic energy was discovered. Based on this linear relationship, the ultimate damage energy can be calculated for sandstone and granite. The evolution of the damage variable based on damage energy was compatible with the real damage condition, which validates the ultimate damage energy calculation method. The research results lay a theoretical foundation for the design and construction of geotechnical engineering. Full article
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23 pages, 6820 KiB  
Article
Apparent Deterioration Law and Shear Failure Mode of Rock–Mortar Interface Based on Topography-Sensing Technology
by Linglin Xie, Wenyu Tang, Hang Lin, Fan Lei, Yifan Chen, Yixian Wang and Yanlin Zhao
Materials 2023, 16(2), 763; https://doi.org/10.3390/ma16020763 - 12 Jan 2023
Viewed by 1286
Abstract
As an advanced spatial technology, topography-sensing technology is comprehensive, macroscopic, and intuitive. It shows unique advantages for rock structure interpretation and has important guiding significance for the research of the shear performances of rock–mortar interface under cyclic load in rock mass engineering. In [...] Read more.
As an advanced spatial technology, topography-sensing technology is comprehensive, macroscopic, and intuitive. It shows unique advantages for rock structure interpretation and has important guiding significance for the research of the shear performances of rock–mortar interface under cyclic load in rock mass engineering. In this paper, cyclic shearing tests combined with the shear surface topography-sensing technology are employed to investigate the evolution characteristics of the interface morphology and the strength deterioration of the rock–mortar interface. Primarily, mortar and three types of rocks are used to prepare different rock–mortar interfaces, which are then applied to cyclic shear loading under two constant normal stresses. Subsequently, the shear strength degradation and dilatancy characteristics of rock–mortar interfaces with varying shear times are discussed. In addition, on the basis of the non-contact three-dimensional topography-sensing technology, the apparent three-dimensional point–cloud coordinate information of rock–mortar interface before and after each shear loading is obtained, and the apparent three-dimensional topography parameters of rock–mortar interface are calculated, according to which the influences of normal stress and lithology on the topography of interface subjected to cyclic shearing loading are analyzed. Full article
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16 pages, 9068 KiB  
Article
Study on Mechanical Properties of Ring Sandstone Specimen under Temperature and Water Coupling Dynamic Compression
by Qi Ping, Qi Gao and Shiwei Wu
Minerals 2023, 13(1), 119; https://doi.org/10.3390/min13010119 - 12 Jan 2023
Cited by 1 | Viewed by 1686
Abstract
The excavation of hard rock roadways in coal mines is often in the environment of underground water and high ground temperature, and it is easy to be affected by the dynamic load, which leads to roadway destruction and increases the difficulty of roadway [...] Read more.
The excavation of hard rock roadways in coal mines is often in the environment of underground water and high ground temperature, and it is easy to be affected by the dynamic load, which leads to roadway destruction and increases the difficulty of roadway support. The ring sandstone specimens with different inner diameters (0~25 mm) were treated with temperature and water coupled, and the dynamic compression test was produced by the Hopkinson pressure rod device (SHPB). The experimental results indicate that the coupling effect of temperature and water reduces the dynamic performance of sandstone specimens. XRD test results showed that the composition of sandstone specimens did not change before and after warm water coupling, and no new substances were found. Dynamic properties of ring sandstone specimens with different inner diameters weaken with the increase in inner diameters. With the increasing inner diameter of ring sandstone specimens, the energy dissipation per unit volume increases the dynamic compressive strength decreases, and the degree of breakage increases. Fracture morphology, average strain rate, and dynamic peak strain of ring sandstone specimens increase with inner diameter. Full article
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18 pages, 4066 KiB  
Article
Fracture Closure Empirical Model and Theoretical Damage Model of Rock under Compression
by Yifan Chen, Hang Lin, Shijie Xie, Rihong Cao, Shuwei Sun, Wenhua Zha, Yixian Wang, Yanlin Zhao and Huihua Hu
Materials 2023, 16(2), 589; https://doi.org/10.3390/ma16020589 - 07 Jan 2023
Cited by 5 | Viewed by 1407
Abstract
The rock or rock mass in engineering often contains joints, fractures, voids, and other defects, which are the root cause of local or overall failure. In response to most of the current constitutive models that fail to simulate the nonlinear fracture compaction deformation [...] Read more.
The rock or rock mass in engineering often contains joints, fractures, voids, and other defects, which are the root cause of local or overall failure. In response to most of the current constitutive models that fail to simulate the nonlinear fracture compaction deformation in the whole process of rock failure, especially brittle rocks, a piecewise constitutive model was proposed to represent the global constitutive relation of rocks in this study, which was composed of the fracture compaction empirical model and the damage statistical constitutive model. The fracture empirical compaction model was determined by fitting the expressions of fracture closure curves of various rocks, while the rock damage evolution equation was derived underpinned by the fracture growth. According to the effective stress concept and strain equivalence hypothesis, the rock damage constitutive model was deduced. The model parameters of the fracture compaction empirical model and damage statistical constitutive model were all calculated by the geometrical characteristics of the global axial stress–strain curve to guarantee that the models are continuous and smooth at the curve intersection, which is also simple and ready to program. Finally, the uniaxial compression test data and the triaxial compression test data of different rocks in previous studies were employed to validate the models, and the determination coefficient was used to measure the accuracy. The results showed great consistency between the model curves and test data, especially in the pre-peak stage. Full article
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20 pages, 4681 KiB  
Review
Research Status and Prospects for the Utilization of Lead–Zinc Tailings as Building Materials
by Rui Li, Ziyi Yin and Hang Lin
Buildings 2023, 13(1), 150; https://doi.org/10.3390/buildings13010150 - 06 Jan 2023
Cited by 6 | Viewed by 2302
Abstract
Lead–zinc tailings are the typical solid wastes in mines with high yield and low utilization rates in some countries at present. They are mainly stockpiled in tailings reservoirs, occupying massive land resources and threatening the health of the environment. One of the advantages [...] Read more.
Lead–zinc tailings are the typical solid wastes in mines with high yield and low utilization rates in some countries at present. They are mainly stockpiled in tailings reservoirs, occupying massive land resources and threatening the health of the environment. One of the advantages of building material production in sustainability is the ability to utilize large amounts of industrial solid wastes, and the use of lead–zinc tailings in building materials is an effective way to meet the dual needs of environmental protection and economic development. This paper reviews the progress of utilizing lead–zinc tailings as building materials and mainly summarizes the status of lead–zinc tailings in cement, geopolymer, concrete, building brick, and foam ceramic. According to previous research, lead–zinc tailings contain large amounts of silica–alumina oxide, which can be used in the production of cement clinker. The addition of lead–zinc tailings to the sintered material can reduce the sintering temperature. The active components contained in lead–zinc tailings can be used in concrete instead of cement or in the preparation of geopolymers. Meanwhile, lead–zinc tailings can also be used as a fine aggregate. However, there are few studies on the durability of building materials with lead–zinc tailings. Additionally, most of the research results of building materials are in the laboratory stage, which are difficult to be promoted. In view of these problems, corresponding suggestions and prospects are given in the end in order to provide a reference for the research on the utilization of lead–zinc tailings. Full article
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14 pages, 6572 KiB  
Article
Mechanism and Application of Layered Grouting Reinforcement for Fractured Coal and Rock Roadway
by Ze Liao and Tao Feng
Appl. Sci. 2023, 13(2), 724; https://doi.org/10.3390/app13020724 - 04 Jan 2023
Cited by 5 | Viewed by 1228
Abstract
This paper takes the ZF3806 working face of Shuiliandong Coal Mine in Binxian County, Shaanxi Province as the engineering background. Aiming at the problems of the development of surrounding rock cracks and roof breakage encountered in the process of roadway excavation and support [...] Read more.
This paper takes the ZF3806 working face of Shuiliandong Coal Mine in Binxian County, Shaanxi Province as the engineering background. Aiming at the problems of the development of surrounding rock cracks and roof breakage encountered in the process of roadway excavation and support and based on the composite beam theory, the method of layered grouting reinforcement of roadways is proposed according to the deformation and failure of the roadway roof and the internal drilling conditions. At the same time, combined with the splitting grouting mechanism, the roadway is strengthened and supported by layered grouting of “shallow bolt grouting + deep cable grouting”. The “shallow” and “deep” form a complete and stable composite beam support structure. After grouting, the bending moments of “shallow” and “deep” support beams decrease by 20.78 × 106 N·m and 26.50 × 106 N·m, respectively. The support scheme is applied to the field test, and the grouting effect is analyzed and monitored. The research results show the layered grouting support scheme of “shallow bolt grouting + deep cable grouting” can significantly improve the structural integrity of the roadway roof. The displacement of the two sides is within the controllable range, and the support role of the bolt and cable is entirely played through grouting. The roof displacement of the roadway is reduced by 65% on average, and the bolt failure and steel belt fracture are significantly reduced, which effectively controls the deformation and damage of the roadway and reduces the maintenance cost of the roadway while ensuring safe mining. The study’s findings could be useful in treating broken surrounding rock in other coal mine roadways. Full article
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15 pages, 5216 KiB  
Article
Study on Stress–Strain Relationship of Coir Fiber-Reinforced Red Clay Based on Duncan–Chang Model
by Xueliang Jiang, Jiahui Guo, Hui Yang, Shufeng Bao, Changping Wen and Jiayu Chen
Appl. Sci. 2023, 13(1), 556; https://doi.org/10.3390/app13010556 - 30 Dec 2022
Cited by 2 | Viewed by 1723
Abstract
Compared with other natural fibers, coir fiber has good strength characteristics and long-term anti-biodegradation ability. At present, most studies on randomly distributed coir fiber-reinforced soil have focused on cohesionless soil or granular soil. In this paper, the influence of randomly distributed coir fiber [...] Read more.
Compared with other natural fibers, coir fiber has good strength characteristics and long-term anti-biodegradation ability. At present, most studies on randomly distributed coir fiber-reinforced soil have focused on cohesionless soil or granular soil. In this paper, the influence of randomly distributed coir fiber on the deviatoric stress and shear strength index of red clay with different fiber content was assessed by a consolidated undrained (CU) triaxial compression test. Since the hyperbolic variational character of the stress–strain relation of the samples conformed to the hyperbolic hypothesis of the Duncan–Chang model of nonlinear elastic model, the Duncan–Chang model was used to fit it, and the influences of fiber content and confining pressure on the parameters of the Duncan–Chang model were studied. The fiber content was determined by testing to be 0%, 0.2%, 0.25%, 0.3%, 0.35% and 0.4% of the dry soil mass. It has been found that coir fiber distributed in a random radial manner can significantly increase the deviatoric stress of red clay, and thus can be effectively used in the case of soil and fiber mixing. The cohesion of the red clay first increases and then decreases with the increase in fiber content, with an optimum content of 0.3%. The internal friction angle changes little with increasing fiber content. Full article
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16 pages, 7121 KiB  
Article
Analysis of Influencing Factors of Cementitious Material Properties of Lead–Zinc Tailings Based on Orthogonal Tests
by Ziyi Yin, Rui Li, Hang Lin, Yifan Chen, Yixian Wang and Yanlin Zhao
Materials 2023, 16(1), 361; https://doi.org/10.3390/ma16010361 - 30 Dec 2022
Cited by 3 | Viewed by 1492
Abstract
At present, the treatment of tailings is mostly carried out in the form of stacking in tailings ponds, resulting in a huge waste of mineral resources and a major threat to the environment and ecology. Using tailings instead of a part of the [...] Read more.
At present, the treatment of tailings is mostly carried out in the form of stacking in tailings ponds, resulting in a huge waste of mineral resources and a major threat to the environment and ecology. Using tailings instead of a part of the cement to make cementitious materials is an effective way to reduce the accumulation of tailings. In this paper, lead–zinc tailings-based cementitious materials were prepared by using lead–zinc tailings, fly ash, and ordinary Portland cement, and the effects of four factors on the mechanical properties of lead–zinc tailings, as well as fly ash content, cement content, and water–binder ratio were studied by orthogonal experiments. The corresponding relationship between the factors and the properties of cementitious materials was determined, and the optimization and prediction of the raw material ratio of lead–zinc tailings-based cementitious materials were realized. The test showed the ratio of raw materials to be at the lowest price ratio. Synchronously the ratio that meets the minimum strength requirements was predicted. When the proportion of fly ash:lead and zinc tailings:cement = 30:40:30 and the water–binder ratio was 0.4, the predicted compressive strength of the prepared cementitious material achieved 22.281 MPa, which meets the strength requirements, while the total content of lead–zinc tailings and fly ash was the highest at this time. Full article
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16 pages, 9673 KiB  
Article
Experimental Study on the Deformation and Mechanical Properties of Bamboo Forest Slopes
by Hui Yang, Zhengyi Cao, Xueliang Jiang and Yixian Wang
Appl. Sci. 2023, 13(1), 470; https://doi.org/10.3390/app13010470 - 29 Dec 2022
Cited by 1 | Viewed by 1159
Abstract
In this paper, model tests on a plain soil slope and a bamboo-rooted slope under slope top loading were carried out to analyze the slope surface displacement, the change in earth pressure, and the failure mode of the slope. Furthermore, the influence of [...] Read more.
In this paper, model tests on a plain soil slope and a bamboo-rooted slope under slope top loading were carried out to analyze the slope surface displacement, the change in earth pressure, and the failure mode of the slope. Furthermore, the influence of rainfall on the deformation and mechanical properties of bamboo-rooted slope sliding was studied. The results show that: (1) the failure mode of the plain soil slope was block sliding failure, while the failure mode of the bamboo-rooted slope was progressive backward failure. (2) Under the slope top load, the slope displacement shows the rule that the top of the slope was large and the foot of the slope was small. The presence of bamboo rhizomes had a negligible effect on the slope displacement, but it significantly contributed to the sliding area’s increase. (3) Compared with the plain soil slope, the earth pressure in the area of the foot of the slope under the same level of the load was elevated more obviously by the bamboo-rooted slope, which indicates that bamboo rhizomes could play a specific role in reinforcing the slope. Still, the scope of its influence was limited and mainly concentrated in the shallow soil. (4) There was a significant increase in the displacement of the bamboo-rooted slope under rainfall conditions, and the magnitude of the upward slope earth pressure was small in the process of step-by-step loading. The test results may have important guiding significance for the in-depth study of the instability law and disaster prevention in bamboo forest areas. Full article
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16 pages, 3217 KiB  
Article
Study on Application of Comprehensive Geophysical Prospecting Method in Urban Geological Survey—Taking Concealed Bedrock Detection as an Example in Dingcheng District, Changde City, Hunan Province, China
by Yu-Long Lu, Chuang-Hua Cao, Yao-Qi Liu and Yang Liu
Appl. Sci. 2023, 13(1), 417; https://doi.org/10.3390/app13010417 - 28 Dec 2022
Cited by 2 | Viewed by 1551
Abstract
In order to ascertain the concealed bedrock and its spatial distribution in an urban low-resistance coverage area of a typical lacustrine basin in Hunan Province, a multi-method comprehensive experimental study was carried out in Dingcheng District, Changde City where there are multiple sets [...] Read more.
In order to ascertain the concealed bedrock and its spatial distribution in an urban low-resistance coverage area of a typical lacustrine basin in Hunan Province, a multi-method comprehensive experimental study was carried out in Dingcheng District, Changde City where there are multiple sets of strata and fault structures. In this study, the wide-area electromagnetic method and microtremor survey were utilized on the basis of traditional methods, including the high-density resistivity method and controlled-source audio-frequency magnetotelluric method, to infer the concealed Cambrian limestone, fault structure, and vertical distribution of strata and the results were verified by drilling. The results indicate that the wide-area electromagnetic method is effective to explore the bedrock and concealed structure in urban geological survey. The microtremor method has an obvious effect on the detection of the Cretaceous and Quaternary silty strata within 100 m. The study may provide references for similar projects in this area. Full article
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21 pages, 8212 KiB  
Article
A Constitutive Model of Time-Dependent Deformation Behavior for Sandstone
by Chongfeng Chen
Materials 2023, 16(1), 135; https://doi.org/10.3390/ma16010135 - 23 Dec 2022
Viewed by 1177
Abstract
Considering sandstone’s heterogeneity in the mesoscale and homogeneity in the macroscale, it is very difficult to describe its time-dependent behavior under stress. The mesoscale heterogeneity can affect the initiation and propagation of cracks. Clusters of cracks have a strong influence on the formation [...] Read more.
Considering sandstone’s heterogeneity in the mesoscale and homogeneity in the macroscale, it is very difficult to describe its time-dependent behavior under stress. The mesoscale heterogeneity can affect the initiation and propagation of cracks. Clusters of cracks have a strong influence on the formation of macroscale fractures. In order to investigate the influence of crack evolution on the formation of fractures during creep deformation, a time-dependent damage model is introduced in this paper. First, the instantaneous elastoplastic damage model of sandstone was built based on the elastoplastic theory of rock and the micro-heterogeneous characteristics of sandstone. A viscoelastic plastic creep damage model was established by combining the Nishihara model and the elastoplastic damage constitutive model. The proposed models have been validated by the results of corresponding analytical solutions. To help back up the model, some conventional constant strain rate tests and multi-step creep tests were carried out to analyze the time-dependent behavior of sandstone. The results show that the proposed damage model can not only reflect the time-dependent viscoelastic deformation characteristics of sandstone, but also provide a good fit to the viscoelastic plastic deformation characteristics of sandstone’s creep behavior. The damage model can also reproduce the propagation process of mesoscopic cracks in sandstone upon the damage and failure of micro-units. This research can provide an effective tool for studying the propagation of microscopic cracks in sandstone. Full article
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22 pages, 53326 KiB  
Article
Mechanical Properties and Failure Behavior of Dry and Water-Saturated Foliated Phyllite under Uniaxial Compression
by Guanping Wen, Jianhua Hu, Yabin Wu, Zong-Xian Zhang, Xiao Xu and Rui Xiang
Materials 2022, 15(24), 8962; https://doi.org/10.3390/ma15248962 - 15 Dec 2022
Cited by 2 | Viewed by 1300
Abstract
Phyllite is widely distributed in nature, and it deserves to be studied considering rock engineering applications. In this study, uniaxial compression tests were conducted on foliated phyllite with different foliation angles under dry and water-saturated conditions. The impacts of water content and foliation [...] Read more.
Phyllite is widely distributed in nature, and it deserves to be studied considering rock engineering applications. In this study, uniaxial compression tests were conducted on foliated phyllite with different foliation angles under dry and water-saturated conditions. The impacts of water content and foliation angle on the stress–strain curves and basic mechanical properties of the Phyllite were analyzed. The experimental results indicate that the peak stress and peak strain decrease first and then increase with increasing foliation angle as a U-shape or V-shape, and the phyllite specimens are weakened significantly by the presence of water. Moreover, an approach with acoustic emission, digital image correlation, and scanning electron microscopic is employed to observe and analyze the macroscopic and mesoscopic failure process. The results show that tensile microcracks dominate during the progressive failure of phyllite, and their initiation, propagation, and coalescence are the main reasons for the failure of the phyllite specimens. The water acts on biotite and clay minerals that are main components of phyllite, and it contributes to the initiation, propagation, and coalescence of numerous microcracks. Finally, four failure modes are classified as followed: (a) for the specimens with small foliation angles α = 0° or 30° (Saturated), both shear sliding and tensile-split across the foliation planes; (b) for the specimens with low to medium foliation angles α = 30° (Dry) or 45°(Saturated), shear sliding dominates the foliation planes; (c) for the specimens with medium to high foliation angles α = 45° (Dry) or 60°, shear sliding dominates the foliation planes; (d) for the specimens with high foliation angles α = 90°, tensile-split dominates the foliation planes. Full article
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17 pages, 4908 KiB  
Article
A Unified Nonlinear Elastic Model for Rock Material
by Chong Chen, Shenghong Chen, Yihu Zhang, Hang Lin and Yixian Wang
Appl. Sci. 2022, 12(24), 12725; https://doi.org/10.3390/app122412725 - 12 Dec 2022
Viewed by 1510
Abstract
Under conditions of low or medium stress, rocks that are in the compression state exhibit perceivable nonlinear elastic characteristics. After a comprehensive review of the existing nonlinear elastic models of rocks and joints, we proposed a new unified nonlinear elastic model. This new [...] Read more.
Under conditions of low or medium stress, rocks that are in the compression state exhibit perceivable nonlinear elastic characteristics. After a comprehensive review of the existing nonlinear elastic models of rocks and joints, we proposed a new unified nonlinear elastic model. This new model contains two parameters with clear definitions, namely, the initial elastic modulus Eni and the modulus change rate m. This model covers a variety of existing models, including the simple exponential model, BB model and two-part Hooke’s model, etc. Based on the RMT experimental system, a large number of uniaxial compression tests for dolomite, granite, limestone and sandstone were performed, and their nonlinear deformation stress‒strain curves were obtained and fit with the unified nonlinear elastic model. The results show that the rocks have obvious nonlinear elastic characteristics in their initial compression stage, and that the unified nonlinear elastic model is able to describe these phenomena rather well. In addition, an empirical formula for predicting the uniaxial compressive strength of the rock was constructed, corresponding to the unified nonlinear elastic model. Full article
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22 pages, 17944 KiB  
Article
Numerical and Experimental Study on a Novel Filling Support Method for Mining of Closely Spaced Multilayer Orebody
by Xiuwen Chi, Zhuojun Zhang, Lifeng Li, Qizhou Wang, Zongying Wang, Haoran Dong and Yu Xie
Minerals 2022, 12(12), 1523; https://doi.org/10.3390/min12121523 - 28 Nov 2022
Cited by 1 | Viewed by 1105
Abstract
Mining of closely spaced multilayer orebodies brings the problems of significant disturbance between adjacent mining layers and drastic structural changes in surrounding rock, which brings the need for a more effective stope support method. Previous research has made sound analysis on filling or [...] Read more.
Mining of closely spaced multilayer orebodies brings the problems of significant disturbance between adjacent mining layers and drastic structural changes in surrounding rock, which brings the need for a more effective stope support method. Previous research has made sound analysis on filling or bolt support, but neither of them can solely provide ideal support effects. Thus, a novel bolt-filling support method is proposed by utilizing the synergistic effect of rock bolts (cable bolts) and filling. Numerical simulation and similarity experiments were conducted in this research to analyze the support effect of this method for multilayer ore mining. For numerical simulation, the distinct-element modelling framework PFC2D (Particle Flow Code in 2 Dimensions) was applied for four support scenarios based on the calibration of the microscopic parameters of particles in vanadium shale ores. The numerical simulation results show that the number of fractures decreases from 1311 without support through 652 with 95% filling support to 410 with bolt-filling support, which is resulted from the redistribution of the force chains due to support change. On the other hand, a 300 cm ×180 cm × 40 cm similarity model with a geometry similarity constant of 100 was established based on the 4# rock layer profile of Mount Shangheng. Two parts of similarity experiments were conducted to investigate the strains around the stopes in multi-layer ore mining for three support scenarios. The experiment results prove that the highest strain is in the center of the roof on the upper goaf, and the roof-bolt filling support induces smaller strains than zero support and conventional filling support. Finally, an effective bolt-filling support system has been developed and validated, which can improve the safety and the stability of the roofs and interlayers during the mining process of closely spaced multilayer orebody by reducing the overall load and fractures in surrounding rock. Full article
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24 pages, 7404 KiB  
Article
Experimental Investigation on Uniaxial Compressive Strength of Thin Building Sandstone
by Baofeng Huang, Yixian Xu and Guojun Zhang
Buildings 2022, 12(11), 1945; https://doi.org/10.3390/buildings12111945 - 10 Nov 2022
Cited by 2 | Viewed by 2270
Abstract
Thin sandstone is a widely used building material; however, its compressive behavior is not well understood. Four groups of cylinders were manufactured in a factory to investigate the uniaxial compressive behavior of red sandstone. Uniaxial compression tests were performed to determine the compressive [...] Read more.
Thin sandstone is a widely used building material; however, its compressive behavior is not well understood. Four groups of cylinders were manufactured in a factory to investigate the uniaxial compressive behavior of red sandstone. Uniaxial compression tests were performed to determine the compressive behavior and failure mode of the specimens. The geometry of the stress–strain diagram varied among the four groups. The critical strain generally increased with a decrease in the height of the cylinder, whereas the compressive strength exhibited an inverse trend. The experimental diagrams were normalized with the peak stress and corresponding critical strain to represent the stress–strain diagram of each group of cylinders. A formula consisting of two parabolas was employed for regression to obtain a representative mathematical expression of the diagram. The correlations between porosity, compressive strength, and elastic modulus were evaluated based on empirical expressions. Normalized strength was employed to evaluate the size effect on the diameter and length–diameter ratio (L/D) of the cylinder; the latter provided a better prediction of the experimental results than the former. A new expression in terms of L/D was proposed based on the regression analysis of the experimental results. This study is beneficial for the engineering application of sandstone as a construction material. Full article
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17 pages, 9161 KiB  
Article
The Freeze-Thaw Strength Evolution of Fiber-Reinforced Cement Mortar Based on NMR and Fractal Theory: Considering Porosity and Pore Distribution
by Chaoyang Zhang, Taoying Liu, Chong Jiang, Zhao Chen, Keping Zhou and Lujie Chen
Materials 2022, 15(20), 7316; https://doi.org/10.3390/ma15207316 - 19 Oct 2022
Cited by 5 | Viewed by 1350
Abstract
Predicting the strength evolution of fiber-reinforced cement mortar under freeze-thaw cycles plays an important role in engineering stability evaluation. In this study, the microscopic pore distribution characteristics of fiber-reinforced cement mortar were obtained by using nuclear magnetic resonance (NMR) technology. The change trend [...] Read more.
Predicting the strength evolution of fiber-reinforced cement mortar under freeze-thaw cycles plays an important role in engineering stability evaluation. In this study, the microscopic pore distribution characteristics of fiber-reinforced cement mortar were obtained by using nuclear magnetic resonance (NMR) technology. The change trend of T2 spectrum curve and porosity cumulative distribution curve showed that the freeze-thaw resistance of cement mortar increased first and then decreased with the fiber content. The optimal fiber content was approximately 0.5%. By conducting mechanical experiments, it is found that the uniaxial compressive strength (UCS) of the samples exhibited the ‘upward convex’ evolution trends with freeze-thaw cycles due to cement hydration, and based on fractal theory, the negative correlation between UCS and Dmin was established. Eventually, a freeze-thaw strength prediction model considering both porosity and pore distribution was proposed, which could accurately predict the strength deterioration law of cement-based materials under freeze-thaw conditions. Full article
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19 pages, 5844 KiB  
Article
Study on Deterioration Characteristics of Uniaxial Compression Performance and Microstructure Changes of Red-Bed Mudstone during Gaseous Water Sorption
by Hongbing Zhu, Zhenghao Fu, Fei Yu and Sai Li
Buildings 2022, 12(9), 1399; https://doi.org/10.3390/buildings12091399 - 06 Sep 2022
Cited by 1 | Viewed by 1686
Abstract
Previously conducted studies have established that gaseous water sorption of mudstone is widespread in nature. The deterioration of its uniaxial compression properties during gaseous water sorption can cause engineering problems. However, related studies were currently in the initial stage of this research direction. [...] Read more.
Previously conducted studies have established that gaseous water sorption of mudstone is widespread in nature. The deterioration of its uniaxial compression properties during gaseous water sorption can cause engineering problems. However, related studies were currently in the initial stage of this research direction. On the one hand, there were few studies on the deterioration characteristics of the uniaxial compression properties of mudstone in this process. The results might not be applicable to all projects. On the other hand, its microstructure changes in this process were unclear. Therefore, to obtain the deterioration characteristics of uniaxial compressive performance during gaseous water sorption for offering scientific reference to the geotechnical engineering of mudstone in the central Sichuan region of China, red-bed mudstone was used as a research material. A swelling test and uniaxial compression tests were carried out. To clarify microstructure changes for advancing the depth of research on the effects of gaseous water on mudstone, scanning electron microscopy (SEM) tests were performed. As a result of this study, formulas were first established that could correctly characterize the deterioration of uniaxial compressive strength (UCS) and elastic modulus when the moisture absorption rate increased. Secondly, the dependence was obtained, which was the relationship between both the UCS and elastic modulus and moisture absorption time. Finally, microstructure changes were revealed during gaseous water sorption. Full article
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17 pages, 6349 KiB  
Article
The Transverse Bearing Characteristics of the Pile Foundation in a Calcareous Sand Area
by Haibo Hu, Lina Luo, Gang Lei, Jin Guo, Shaoheng He, Xunjian Hu, Panpan Guo and Xiaonan Gong
Materials 2022, 15(17), 6176; https://doi.org/10.3390/ma15176176 - 05 Sep 2022
Cited by 2 | Viewed by 1507
Abstract
Reviewing literature revealed that the studies on the bearing characteristics of pile foundations mainly focuses on clay, ordinary sand, loess, saline soil, and other areas. However, few studies on the bearing characteristics of the pile foundation in calcareous sand were conducted. Besides, existing [...] Read more.
Reviewing literature revealed that the studies on the bearing characteristics of pile foundations mainly focuses on clay, ordinary sand, loess, saline soil, and other areas. However, few studies on the bearing characteristics of the pile foundation in calcareous sand were conducted. Besides, existing traditional studies ignored the variation of soil compression modulus with depth, and the effect of void ratio on the transverse bearing characteristics of the pile foundation in a calcareous sand area were not well understood. In response of these problems, this study conducted a theoretical investigation on the transverse bearing characteristics of the pile foundation in a calcareous sand area. The transverse bearing characteristics of the pile foundation were derived based on the Pasternak foundation model and the Winkler foundation model, incorporating the heterogeneous distribution of compressive modulus with buried depth. The calculation results of the Pasternak foundation model are closer to the observed results than the Winkler foundation model. Therefore, the following research on the transverse bearing characteristics of the pile foundation in the calcareous sand area adopts the Pasternak foundation model. Then, the effects of the pile length, pile diameter, pile elastic modulus, horizontal load, bending moment, and void ratio on the transverse bearing characteristics of the pile foundation in a calcareous sand area were thoroughly analyzed. Furthermore, the difference between the transverse bearing characteristics of the pile foundation in a calcareous sand area and a quartz sand area was discussed. Results show that the horizontal displacement of the pile top in a calcareous sand area is greater than the quartz sand area under the same conditions. Full article
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15 pages, 2012 KiB  
Article
Microseismic Source Location Method and Application Based on NM-PSO Algorithm
by Ze Liao, Tao Feng, Weijian Yu, Dongge Cui and Genshui Wu
Appl. Sci. 2022, 12(17), 8796; https://doi.org/10.3390/app12178796 - 01 Sep 2022
Cited by 3 | Viewed by 1501
Abstract
Microseismic source location is the core of microseismic monitoring technology in coal mining; it is also the advantage of microseismic monitoring technology compared with other monitoring methods. The source location method directly determines the accuracy and stability of the source location results. Based [...] Read more.
Microseismic source location is the core of microseismic monitoring technology in coal mining; it is also the advantage of microseismic monitoring technology compared with other monitoring methods. The source location method directly determines the accuracy and stability of the source location results. Based on the problem of non-benign arrays of microseismic monitoring sensors in the coal mining process, a fast location method of microseismic source in coal mining based on the NM-PSO algorithm is proposed. The core idea of the NM-PSO algorithm is to use the particle swarm optimization (PSO) algorithm for global optimization, reduce the size of the solution space and provide the optimized initial value for the Nelder Mead simplex algorithm (NM), and then use the fast iteration characteristics of the NM algorithm to accelerate the convergence of the model. The NM-PSO algorithm is analyzed by an example and verified by the microseismic source location engineering. The NM-PSO algorithm has a significant improvement in the source location accuracy. The average location errors in all directions are (5.65 m, 5.01 m, and 7.21 m), all Within the acceptable range, and they showed good universality and stability. The proposed NM-PSO algorithm can provide a general fast seismic source localization method for different sensor array deployment methods, which significantly improves the stability and result in the accuracy of the seismic source localization algorithm and has good application value; this method can provide new ideas for research in microseismic localization in coal mining. Full article
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15 pages, 5960 KiB  
Article
Development of Damage Type Viscoelastic Ontological Model for Soft and Hard Materials under High-Strain-Rate Conditions
by Wei Liu, Xiangyun Xu and Chaomin Mu
Appl. Sci. 2022, 12(17), 8407; https://doi.org/10.3390/app12178407 - 23 Aug 2022
Cited by 4 | Viewed by 1364
Abstract
By improving the ZWT model, a principal structure model applicable to both soft and hard materials under dynamic loading conditions was obtained. Dynamic mechanical experiments were conducted using SHPB to obtain stress–strain curves for coal rock and foam concrete. The ZWT intrinsic model [...] Read more.
By improving the ZWT model, a principal structure model applicable to both soft and hard materials under dynamic loading conditions was obtained. Dynamic mechanical experiments were conducted using SHPB to obtain stress–strain curves for coal rock and foam concrete. The ZWT intrinsic model was simplified according to the dynamic impact characteristics of concrete, and the intrinsic model was established by introducing macroscopic damage quantity D and correction factor δ. The stress–strain curves of coal rock, foamed concrete, steel fiber concrete, granite, lightweight foamed concrete, and EPS concrete at different strain rates were used to validate the present constitutive model and prove the correctness of the model. Full article
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19 pages, 7330 KiB  
Article
Wavelet Energy Evolution Characteristics of Acoustic Emission Signal under True-Triaxial Loading during the Rockburst Test
by Chuanyu Hu, Fuding Mei and Wakeel Hussain
Appl. Sci. 2022, 12(15), 7786; https://doi.org/10.3390/app12157786 - 02 Aug 2022
Viewed by 1238
Abstract
The rockburst simulation test is conducted by utilizing a mineral-containing marble specimen. The loading condition is set to the three directions, each loading on five surfaces except for a single free surface. The whole test procedure is monitored in real time by using [...] Read more.
The rockburst simulation test is conducted by utilizing a mineral-containing marble specimen. The loading condition is set to the three directions, each loading on five surfaces except for a single free surface. The whole test procedure is monitored in real time by using a PCI-II acoustic emission monitoring system and a high-speed camera. According to the test outcomes, rockburst is a process in which energy is rapidly released from the free surface. Rock block and rock plate are buckled and ejected from the free surface and a severe rockburst process is accompanied by spray rock powder. An explosion sound can be heard during the process, which can be analyzed by signal processing techniques. The failure mode of the specimen is a splitting-shearing composite failure, and the free surface becomes a rockburst destruction surface. A V-type rockburst pit is formed in the ejection area. The effective acoustic emission signal of the whole test process is decomposed and reconstructed using five-layer wavelets to produce six frequency band sub-signals. In addition, the wavelet energy and its energy distribution coefficients are assessed for various frequency bands, and the proportion of each dominant frequency band within each period is computed. Finally, it was found that the dominant frequency band is 125~250 kHz, while the suboptimal frequency band is 250~500 kHz. The succeeding features are noticed to be used as predicted features for the rockburst disaster. Namely, acoustic emission signals arise in large numbers and the energy distribution coefficient of the dominant frequency band concentrates above 0.4. The proportion of dominant frequency band appears in continuous valley type and keeps below 80%, while the proportion of suboptimal frequency band appears in continuous peak type and keeps above 20%. Full article
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21 pages, 4785 KiB  
Article
Numerical Analysis of Microcrack Propagation Characteristics and Influencing Factors of Serrated Structural Plane
by Xing Zhang, Hang Lin, Jianxin Qin, Rihong Cao, Shaowei Ma and Huihua Hu
Materials 2022, 15(15), 5287; https://doi.org/10.3390/ma15155287 - 31 Jul 2022
Cited by 4 | Viewed by 1371
Abstract
The serrated structural plane is the basic unit of structural plane morphology. However, the understanding of its internal stress distribution, failure mode and crack evolution law was not clear enough in previous studies. In this paper, the shear mechanical properties of the serrated [...] Read more.
The serrated structural plane is the basic unit of structural plane morphology. However, the understanding of its internal stress distribution, failure mode and crack evolution law was not clear enough in previous studies. In this paper, the shear mechanical properties of the serrated structural planes were studied by numerical simulation, and the crack evolution law of the serrated structural planes and the effects of four microscopic parameters on the shear properties were analyzed. The results show that: (1) the number of microcracks increases with the increase in normal stress; the crack expansion rate is slow before the shear stress reaches the peak. After the shear stress reaches the peak, the crack expansion rate continues to increase, and the microcracks keep sprouting and expanding, and the number of microcracks tends to stabilize when the shear stress reaches the residual shear strength. (2) The particle contact stiffness ratio kn/ks and parallel bond stiffness ratio kn/ks were negatively correlated with the shear strength; and the particle contact modulus E and parallel bond modulus E were positively correlated with the shear strength. As the particle contact modulus E and parallel bond modulus E increase, the peak shear displacement gradually decreases. The parallel bond stiffness ratio kn/ks has a negative correlation with the peak shear displacement. This study is expected to provide theoretical guidance for the microscopic parameter calibration and shear mechanical analysis of serrated structural planes. (3) Several XGBoost, WOA-XGBoost, and PSO-XGBoost algorithms are introduced to construct the quantitative prediction model, and the comparative analysis found that WOA-XGBoost has the best fitting effect and can be used for the prediction of shear strength. When using this model to calculate the weight shares of micro-parameters, it was found that kn/ks has the greatest influence on shear strength, followed by E; E and kn/ks had the least influence. Full article
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22 pages, 10385 KiB  
Article
Deformation and Force Analysis of Wood-Piled Island Cofferdam Based on Equivalent Bending Stiffness Principle
by Shi Chen, Yixian Wang, Yonghai Li, Xian Li, Panpan Guo, Weichao Hou and Yan Liu
Buildings 2022, 12(8), 1104; https://doi.org/10.3390/buildings12081104 - 27 Jul 2022
Cited by 2 | Viewed by 1830
Abstract
This paper analyses the deformation and force behavior of a wood-piled island cofferdam based on the principle of equivalent bending stiffness. The horizontal deformation and bending moments in wood piles and the axial stress in tension bars on top of piles were both [...] Read more.
This paper analyses the deformation and force behavior of a wood-piled island cofferdam based on the principle of equivalent bending stiffness. The horizontal deformation and bending moments in wood piles and the axial stress in tension bars on top of piles were both analyzed by the finite difference (FD) method. Except for the analysis of the cofferdam construction process, the influence of the pile length, the dam width, the tension bar interval, and the pile interval, among the commonly adopted parameters, were detailly examined in numerical simulations. In addition, a reinforced wood-piled cofferdam model by steel pipe piles has been established to quantify the effect of reinforcement. It was found that the dewatering inside the cofferdam was detrimental to cofferdam stability. The pile deformation reached maxima (roughly 0.6% of the pile length) at solidifying stage after dewatering. The changing trend of the cofferdam structure force within a safe district was consistent with the displacement. The dam width had a vital effect on the stability of the cofferdam, especially on the horizontal deformation. The steel pipe pile reinforcement scheme performed better in further deformation control, providing a new idea for island-type cofferdams with rigorous structural deformation control. Full article
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14 pages, 39785 KiB  
Article
Physical and Thermal Properties Analysis of Hematite for Thermal Heat Storage
by Andreia Santos, Fernando Almeida and Fernando Rocha
Materials 2022, 15(13), 4648; https://doi.org/10.3390/ma15134648 - 01 Jul 2022
Cited by 1 | Viewed by 1817
Abstract
Energy sustainability represents an important research topic for aiding decreasing energy dependence and slowing down climate changes. In this context, solutions using thermal energy storage through rock start to emerge, due to its natural benefits, when compared to more polluting alternatives. To understand [...] Read more.
Energy sustainability represents an important research topic for aiding decreasing energy dependence and slowing down climate changes. In this context, solutions using thermal energy storage through rock start to emerge, due to its natural benefits, when compared to more polluting alternatives. To understand whether a rock material can be considered a good thermal energy storage material for such solutions, it is necessary to evaluate the physical, chemical and thermal properties of such materials. Therefore, it becomes essential to understand how heat propagates in the rock and how voids influence the thermal properties. To achieve these goals, hematite ore from Moncorvo, Northeastern Portugal was used, in particular, to study the effect of grain size on thermal properties for three different sized lots. Chemical and physical changes between heated and unheated lots were detected using X-ray diffraction and particle size, as well as X-ray fluorescence analysis. Regarding thermal properties, a hot wire method approach was used with seven thermocouples. Additionally, a thermal inversion model to simulate the heat exchanges was also proposed, allowing changing the properties of the constituents, to fit the theoretical and experimental temperature curve. Furthermore, the model reveals how heat propagates inside the reservoir filled with hematite ore. Full article
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17 pages, 3523 KiB  
Article
Influence of Morphology Characteristics on Shear Mechanical Properties of Sawtooth Joints
by Huihua Hu, Xing Zhang, Jianxin Qin and Hang Lin
Buildings 2022, 12(7), 886; https://doi.org/10.3390/buildings12070886 - 22 Jun 2022
Cited by 2 | Viewed by 1616
Abstract
The interface problem exists widely in building. Joints are interfaces of rock mass structures. To further study the influence of morphological characteristics on the shear mechanical properties of sawtooth joints, this paper prepared rock-like materials based on the similarity principle and carried out [...] Read more.
The interface problem exists widely in building. Joints are interfaces of rock mass structures. To further study the influence of morphological characteristics on the shear mechanical properties of sawtooth joints, this paper prepared rock-like materials based on the similarity principle and carried out direct shear tests of sawtooth joints. The results showed that: (1) the peak shear displacement of joints first increases and then decreases with increasing normal stress, but the normal trend of stress during turning is different under different sawtooth angles. When the sawtooth angle of the joints is small, the decrease in shear stress between shear strength and residual shear strength is not obvious, and the rate of decrease is also small. (2) The shear strength of joints is positively correlated with normal stress. Using the Mohr–Coulomb criterion to analyze the shear strength of joints, it was found that the cohesion c and internal friction angle α of joints increased nonlinearly with increasing sawtooth angle, but their increasing trends were different. By introducing the function relation between cohesion, internal friction angle, and sawtooth angle into the classical shear strength equation, an empirical equation for the shear strength of joints was established in consideration of sawtooth angle. (3) There are two modes of shear failure for serrated joints: the “saw-toothed sliding gnawing failure mechanism” (SSG) and the “tensile fracture mechanism” (TFM). In the SSG, the shear failure mode of joints evolves in a slipping–gnawing–complete gnawing mechanism with increasing sawtooth angle and normal stress. The TFM mainly occurs at high sawtooth angles. This study provides a theoretical reference for the prediction and prevention of geological disasters. Full article
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18 pages, 5842 KiB  
Article
Numerical Simulation of Flood Intrusion Process under Malfunction of Flood Retaining Facilities in Complex Subway Stations
by Zhiyu Lin, Shengbin Hu, Tianzhong Zhou, Youxin Zhong, Ye Zhu, Lei Shi and Hang Lin
Buildings 2022, 12(6), 853; https://doi.org/10.3390/buildings12060853 - 19 Jun 2022
Cited by 11 | Viewed by 2465
Abstract
In recent years, heavy rain and waterlogging accidents in subway stations have occurred many times around the world. With the comprehensive development trend of underground space, the accidents caused by flood flow intruding complex subway stations and other underground complexes in extreme precipitation [...] Read more.
In recent years, heavy rain and waterlogging accidents in subway stations have occurred many times around the world. With the comprehensive development trend of underground space, the accidents caused by flood flow intruding complex subway stations and other underground complexes in extreme precipitation disasters will be lead to more serious casualties and property damage. Therefore, it is necessary to conduct numerical simulation of flood intrusion process under malfunction of flood retaining facilities in complex subway stations. In order to prevent floods from intruding subway stations and explore coping strategies, in this study, the simulation method was used to study the entire process of flood intrusion into complex subway stations when the flood retaining facilities fail in extreme rain and flood disasters that occur once-in-a-century. The three-dimensional numerical simulation model was constructed by taking a subway interchange station with a property development floor in Nanning as a prototype. Based on the Volume of Fluid (VOF) model method, the inundated area in the subway station during the process of flood intrusion from the beginning to the basic stability was simulated, and it was found that the property development floor has serious large-scale water accumulation under extreme rainfall conditions. Through the dynamic monitoring of the flood water level depth at important positions such as the entrances of the evacuation passages, and the analysis of the influence of the design structure and location distribution of different passages on the personnel evacuation plan, it was found that the deep water accumulation at the entrances of the narrow, long, and multi-run emergency safety passages are not conducive to the evacuation of personnel. Finally, the flow of flood water into the subway tunnel through the subway station was calculated. The research results provide certain reference and guidance for the safety design of subway stations under extreme rainfall climatic conditions. Full article
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