Geomechanics and Geotechnical Engineering Problems in the Design and Construction of Underground Buildings

A special issue of Buildings (ISSN 2075-5309). This special issue belongs to the section "Building Structures".

Deadline for manuscript submissions: 20 July 2024 | Viewed by 13190

Special Issue Editors

School of Civil Engineering, Chang’an University, Xi'an 710061, China
Interests: stress waves propagation in jointed rock mass; mechanical properties and damage characteristics of discontinuous rock mass; engineering rock disaster prevention and mitigation; dynamic response of underground structure
Institution of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
Interests: static and dynamic constitutive model of rock materials; mechanical properties of rock materials; stability of slope and landslide; dynamic response and mechanical mechanism analysis of underground rock engineering; numerical calculation and finite element programming
National Inland Waterway Regulation Engineering Research Center, Chongqing Jiaotong University, Chongqing 400074, China
Interests: rock damage mechanics; surrounding rock stability control; dynamic response of underground structure; soil interacts with structure
School of Civil and Hydraulic Engineering, Ningxia University, Yinchuan 750021, China
Interests: loess mechanics; soil structural characteristics; loess foundation-superstructure interaction

Special Issue Information

Dear Colleagues,

The fact that underground engineering is located or partially located below the surface determines that the geotechnical problems of underground engineering will run through the whole life cycle of underground engineering, including site selection, planning, investigation, design, construction, use, maintenance, transformation, reinforcement, demolition and restoration. At present, the construction schemes of underground engineering are classified into open excavation method, shallow buried excavation method, cover excavation method, drilling and blasting method, road header method, shield method, pipe jacking method, buried pipe section method, caisson method, trenchless technology scheme and so on. For underground engineering, geomechanics and geotechnical problems have the whole process, extensive and particularity.

The Special Issue titled "Geomechanics and Geotechnical Engineering Problems in the Design and Construction of Underground Buildings" will accept manuscripts covering a wide range of topics, from basic research to more applied exploration and comprehensive case studies.  Topics include, but are not limited to:

  1. Interaction between soil and structure;
  2. Safety and stability of underground structure;
  3. Earthquake resistance of underground structure;
  4. Mechanical properties and constitutive models of engineering rock, soil or concrete materials;
  5. Geotechnical engineering problems in underground engineering construction;
  6. Geotechnical properties and engineering applications under regional or special environment;
  7. Stress wave propagation and attenuation law in rock and soil mass;
  8. Theory and technology of rock breaking by explosion and dynamic load;
  9. Response and disaster mechanism of underground engineering under engineering disturbance;
  10. Other topics.

Dr. Shaobo Chai
Dr. Yongqiang Zhou
Dr. Erdi Abi
Dr. Longlong Lv
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Buildings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • underground buildings engineering
  • rock and soil mechanics
  • geotechnical engineering
  • seismic resistance of underground structure
  • mechanical property
  • regional geological environment
  • seismic response
  • engineering disturbance
  • constitutive model

Published Papers (17 papers)

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Research

17 pages, 10563 KiB  
Article
A Study on Seismic Dynamic Response of Pile-Supported Tunnels in Deep Backfill Area of Soil–Rock Mixture Based on a Model Test
by Hanlin Li, Xiaoguang Jin, Guodong Sun and Jie He
Buildings 2024, 14(3), 791; https://doi.org/10.3390/buildings14030791 - 14 Mar 2024
Viewed by 324
Abstract
Aiming to address the problem of construction and environmental risks in tunnel construction through the soil–rock mixture backfill area, this paper carried out a seismic dynamic response model test of a pile-supported tunnel based on practical projects. Firstly, the stress–strain curves and failure [...] Read more.
Aiming to address the problem of construction and environmental risks in tunnel construction through the soil–rock mixture backfill area, this paper carried out a seismic dynamic response model test of a pile-supported tunnel based on practical projects. Firstly, the stress–strain curves and failure characteristics of the soil–rock mixture in the study area were obtained through triaxial tests, and based on this, similar materials for the model test were developed. Then, a vibration table model test was devised to investigate the seismic dynamic response of the pile–tunnel structure. The findings revealed the following: when subjected to seismic waves, the soil–rock mixture stratum displayed a “skin effect” in its acceleration response, indicating that closer proximity to the surface led to heightened horizontal acceleration responses; the horizontal peak acceleration of the grouting mixture stratum in the vertical direction exhibited a “Zigzag” pattern; the peak values of strain response and bending moment in the tunnel lining cross-section exhibited an “X” shape and inverted “V” shape, respectively. The bending moment at the pile crown increased alongside the peak value of the input seismic wave acceleration. The maximum surface settlement in the model ranged from 0.5 to 1 cm, with the tunnel–pile structure effectively mitigating surface settlement. Full article
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23 pages, 15032 KiB  
Article
Hybrid Effect of Basalt and Polyacrylonitrile Fibers on Physico-Mechanical Properties of Tailing Mortar
by Jianbo Xu, Zhijie Pi, Shibing Huang, Yanzhang Liu, Ziwen Chen and Yongqi Shen
Buildings 2024, 14(3), 639; https://doi.org/10.3390/buildings14030639 - 29 Feb 2024
Viewed by 394
Abstract
In this study, 50% iron ore tailings (IOTs) were used to prepare the cemented mortar at low economic costs and with great environmental benefits. Basalt fiber (BF) and polyacrylonitrile fiber (PANF) were added to the tailing mortar to improve the comprehensive performance of [...] Read more.
In this study, 50% iron ore tailings (IOTs) were used to prepare the cemented mortar at low economic costs and with great environmental benefits. Basalt fiber (BF) and polyacrylonitrile fiber (PANF) were added to the tailing mortar to improve the comprehensive performance of tailing mortars, including BF (0~0.5%), PANF (0~0.05%) and the combination of them. The results show that the addition of BF and PANF can significantly improve the ultrasonic velocity, uniaxial compressive strength (UCS), split-tensile strength (STS), flexural strength (FS) and toughness of the tailing mortar. A novel finding is that the enhancement of hybrid fibers is much better than single fiber, and the best hybrid fiber combination is B0.25P0.05 (0.25 wt% BF and 0.05 wt% PANF), because this combination not only causes the most considerable increase in strength but also possesses great cost-effectiveness. Compared to the B0P0 group without fibers, the maximum increments of B0.25P0.05 in UCS, STS and FS are 45.74%, 52.33% and 15.65%, respectively. It is evidenced that the improvement in STS is the largest because the fibers have good cracking resistance and bridging effect in the tailing mortar. The scanning electron microscope (SEM) further confirms that too many hybrid fibers will agglomerate and produce more voids, which is harmful to the development of the internal structure. Beyond B0.25P0.05, the hydration products are also reduced due to the decrease in nucleation sites, observed by combining X-ray diffraction (XRD) tests. Therefore, it is suggested that the hybrid fibers containing 0.25% BF and 0.05% PANF should be used in this tailing mortar. Full article
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12 pages, 6470 KiB  
Article
Investigation of the Disintegration Characteristics of Neogene Mudstone at Different Burial Depths
by Liang Peng, Wenxue Du, Ganggang Bai, Lahuancairang, Shixiang Yuan, Juntao Li and Peng Feng
Buildings 2024, 14(1), 227; https://doi.org/10.3390/buildings14010227 - 15 Jan 2024
Viewed by 457
Abstract
The complex structure of Neogene mudstone plays an important role in geological disasters. A close relationship exists between the mechanisms of mudstone landslides and the disintegration characteristics of rocks. Therefore, understanding the disintegration characteristics of Neogene mudstone at different depths is crucial for [...] Read more.
The complex structure of Neogene mudstone plays an important role in geological disasters. A close relationship exists between the mechanisms of mudstone landslides and the disintegration characteristics of rocks. Therefore, understanding the disintegration characteristics of Neogene mudstone at different depths is crucial for enhancing engineering safety and assessing landslide stability. This study employed Neogene mudstone from different depths to perform disintegration and plastic limit experiments and revealed the sliding mechanisms of landslides involving Neogene mudstone, providing theoretical support for mitigating mudstone geological disasters. Our results demonstrate that Neogene mudstone from different depths experiences varied stress conditions and pore water pressure due to geological actions, significantly affecting the disintegration characteristics. By ignoring the factors of the slip surface, the slake durability index of mudstone decreases with increasing burial depth, while the plasticity limit index tends to rise. The influence of groundwater, geo-stress, and pore structure on Neogene mudstones at different depths results in overall weak stability and disintegration. Landslide occurrences are likely connected to the mechanical properties of mudstones at the slip surface, where a low slake durability index and higher plasticity index make the mudstones prone to fracturing, breaking, and disintegrating once in contact with water. Full article
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17 pages, 14560 KiB  
Article
The Mechanical Behavior and Constitutive Model Study of Coarse-Grained Soil under Cyclic Loading–Unloading in Large-Scale Plane Strain Conditions
by Zhi Wang, Shuai Shao, Shengjun Shao and Liguo Yang
Buildings 2024, 14(1), 200; https://doi.org/10.3390/buildings14010200 - 12 Jan 2024
Viewed by 496
Abstract
To address loading and unloading issues in civil and hydraulic engineering projects that employ coarse-grained soil as fill material under plane strain conditions during construction and operation, cyclic loading–unloading large-scale plane strain tests were conducted on two types of coarse-grained soils. The effects [...] Read more.
To address loading and unloading issues in civil and hydraulic engineering projects that employ coarse-grained soil as fill material under plane strain conditions during construction and operation, cyclic loading–unloading large-scale plane strain tests were conducted on two types of coarse-grained soils. The effects of coarse-grained soil properties on shear behavior and various modulus relationships were analyzed. The research results showed that coarse-grained soils with better particle roundness exhibit significant shear dilation deformation; it was also found that low parent rock strength can lead to strain softening, and an increase in confining pressure suppresses shear dilation deformation. During the cyclic loading–unloading process, the initial unloading modulus (Eiu) > unloading–reloading modulus (Eur) > initial reloading modulus (Eir) > initial tangent modulus (Ei), with the unloading modulus considerably greater than the others. In finite element simulations and model calculations, it is essential to select appropriate modulus parameters based on the stress conditions of the soil to ensure calculation accuracy. In this work, an elastoplastic and nonlinear elastic theory was used to establish a cyclic loading–unloading constitutive model. By comparing the values obtained using this model with experimental measurements, it was found that the model can reasonably predict stress–strain variations during cyclic loading–unloading of coarse-grained soils under plane strain conditions. Full article
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31 pages, 11304 KiB  
Article
Field Tests and the Numerical Analysis of a Pile-Net Composite Foundation for an Intelligent Connected Motor-Racing Circuit
by Xiaonan Wang and Qitao Pei
Buildings 2024, 14(1), 174; https://doi.org/10.3390/buildings14010174 - 10 Jan 2024
Viewed by 470
Abstract
In response to the problem of significant post-construction settlement that may occur in a motor racing circuit (MRC), two representative composite foundation testing areas, PHC pile (pre-tensioned spun high-strength concrete pile) and CFG pile (cement fly ash gravel pile), were selected for field [...] Read more.
In response to the problem of significant post-construction settlement that may occur in a motor racing circuit (MRC), two representative composite foundation testing areas, PHC pile (pre-tensioned spun high-strength concrete pile) and CFG pile (cement fly ash gravel pile), were selected for field tests to obtain the deformation law of pile–soil. Then, finite element numerical simulation was used to carry out back analysis on the geological mechanical parameters of the testing areas. The results showed that the error of soil settlement between the piles in the PHC pile and CFG pile testing areas were 8.2% and 9.6%, respectively, with good inversion precision. The obtained geological mechanical parameters can be used to predict the settlement of the rest of the MRC. On this basis, a finite element numerical model was constructed to analyze the bearing and deformation characteristics of the foundation of the MRC under five types of working conditions that may cause significant post-construction settlement. It showed that the settlement of the embankment was large in the middle and small on both sides after the consolidation of the embankment. The maximum settlement was about 27.0 mm, and the maximum longitudinal uneven settlement ratio of the embankment was 1.3/4000. The axial force of piles in the PHC pile and CFG pile composite foundations increased first and then decreased with depth. The maximum bending moment was located at the foot of slopes or at the boundary of strata, which was relatively small in the middle of the embankment. The deformation of the embankment and the bearing capacity of the piles could meet engineering requirements. This study has certain guiding significance for the design and construction of similar pile-net composite foundations. Full article
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29 pages, 10735 KiB  
Article
Influence of Different Construction Methods on Lateral Displacement of Diaphragm Walls in Large-Scale Unsupported Deep Excavation
by Hao-Wei Chiu, Chia-Feng Hsu, Fu-Huan Tsai and Shong-Loong Chen
Buildings 2024, 14(1), 23; https://doi.org/10.3390/buildings14010023 (registering DOI) - 21 Dec 2023
Viewed by 578
Abstract
This study examines the influence of different construction methods on the lateral displacement of diaphragm walls in large-scale, unsupported deep excavations. Using the three-dimensional finite element method (FEM) with PLAXIS 3D 2017 software, the research assesses how varying construction techniques impact wall stability, [...] Read more.
This study examines the influence of different construction methods on the lateral displacement of diaphragm walls in large-scale, unsupported deep excavations. Using the three-dimensional finite element method (FEM) with PLAXIS 3D 2017 software, the research assesses how varying construction techniques impact wall stability, particularly in proximity to sensitive structures like metro systems. The project uniquely integrates peripheral top-down and central bottom-up approaches to minimize environmental disruption. Key focus areas include the roles of back-pull slabs, zoned excavation, and cross walls in reducing wall deformation. Findings reveal that zoned excavation significantly controls lateral displacement on longer site sides, enhancing adjacent structure safety and overall construction integrity. Back-pull slabs are shown to effectively decrease top wall deformation, thereby increasing structural stiffness. Moreover, despite their considerable length (nearly 60 m), cross walls play a crucial role in controlling lateral deformation along the excavation’s length. These insights offer valuable guidance for future projects, especially in regions like Taiwan, where experience with such large-scale, unsupported excavations is limited. Full article
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14 pages, 6928 KiB  
Article
Numerical Simulation of Impact Effect on Stability of Transmission Tower Foundation
by Lang Song, Shaobo Chai, Lianzeng Chai, Xianpeng Li and Jinhao Liu
Buildings 2023, 13(12), 3047; https://doi.org/10.3390/buildings13123047 - 07 Dec 2023
Viewed by 574
Abstract
The impact effect can cause structural damage to a transmission tower’s foundation and affect its overall stability. In order to study the influence of the impact effect on the stability of transmission tower foundations, a three-dimensional finite element numerical simulation method was used [...] Read more.
The impact effect can cause structural damage to a transmission tower’s foundation and affect its overall stability. In order to study the influence of the impact effect on the stability of transmission tower foundations, a three-dimensional finite element numerical simulation method was used to investigate the variations in the extent of damage, displacement, and inclination degree of a transmission tower foundation under different impact velocities, impact durations, impactor shapes, and impact locations. The results show that as the impact velocity increases, the damage value of the transmission tower foundation continuously increases, and the damaged area expands. The lateral displacement value increases continuously with the duration of the impact effect, and the variation in lateral displacement follows a linear function distribution. The inclination degree of the transmission tower foundation increases continuously with increased impact duration and can lead to overturning failure. A smaller impact contact area results in a larger compressive damage value for the transmission tower foundation, and different impact contact areas lead to different modes of failure for the transmission tower foundation. The damage value and damaged area of the transmission tower foundation vary with the location of the impact. By comparing the deformation of the transmission tower foundation before and after reinforcement, it is evident that the reinforcement design can significantly improve the deformation resistance and anti-overturning capacity of the transmission tower foundation. Full article
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28 pages, 7105 KiB  
Article
Three-Dimensional Numerical Analysis on the Influence of Buttress Wall Removal Timing on the Lateral Deformation of Diaphragm Walls during Deep Excavation
by Chia-Feng Hsu, Chung-Fu Kuan and Shong-Loong Chen
Buildings 2023, 13(11), 2678; https://doi.org/10.3390/buildings13112678 - 24 Oct 2023
Viewed by 735
Abstract
Urban areas in Taiwan are densely populated with limited land. Excavation often takes place near existing buildings, necessitating protective measures for adjacent properties. Among these measures, cross walls or buttress walls are commonly employed, especially in weak foundation soils, which have seen many [...] Read more.
Urban areas in Taiwan are densely populated with limited land. Excavation often takes place near existing buildings, necessitating protective measures for adjacent properties. Among these measures, cross walls or buttress walls are commonly employed, especially in weak foundation soils, which have seen many successful applications. These mechanisms mainly contribute to reducing lateral deformation of the diaphragm walls, ground subsidence, and excavation face uplift. However, the behavior of these walls is essentially three-dimensional, and common engineering analyses employing one-dimensional elastoplastic beam analysis cannot adequately simulate their mechanical behavior. This study utilized the PLAXIS 3D 2018 software to analyze real-life cases of buttress walls and cross walls. Then, the results of the numerical models were validated against actual field measurements, and the outcomes were satisfactory, and within the regulatory allowable values. The primary objective of this study was to find the influence of different buttress wall removal timings on the lateral deformation of the diaphragm wall. The findings suggest that the gradual removal of buttress walls will effectively control the lateral deformation of diaphragm walls during the excavation of deeper floors like mezzanines. Full article
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22 pages, 4586 KiB  
Article
Study on the Influence of a Rubber-Modified Soil Isolation Layer on the Isolation Performance of Frame Structures with Different Foundation Forms
by Shaoqiang Chai, Yong Chen, Dongbo Cai, Wei Wang, Qihao Chen and Jinhao Liu
Buildings 2023, 13(10), 2584; https://doi.org/10.3390/buildings13102584 - 13 Oct 2023
Viewed by 456
Abstract
In order to investigate the seismic performance of a rubber-modified soil isolation layer, a three-dimensional finite element model was constructed using finite element analysis software, utilizing a two-story frame structure as the engineering background. Nonlinear dynamic time history analysis and comparisons were performed [...] Read more.
In order to investigate the seismic performance of a rubber-modified soil isolation layer, a three-dimensional finite element model was constructed using finite element analysis software, utilizing a two-story frame structure as the engineering background. Nonlinear dynamic time history analysis and comparisons were performed against the seismic performance of the structure. The evaluation was based on several parameters, including the contact area of the base, the thickness of the rubber-particle-modified soil isolation layer, ground motion records with varying amplitudes, and seismic frequency spectrum characteristics. The research findings indicate that the implementation of a rubber-modified soil isolation layer effectively mitigates the peak acceleration, horizontal displacement, and shear stress of the frame structure. This not only enhances the seismic performance of the structure but also enlarges the contact area of the base. Increasing the thickness of the rubber-modified soil isolation layer will effectively decrease the peak acceleration, horizontal displacement, and shear stress of the structure during seismic events. The effectiveness of the isolation provided by the rubber-modified soil layer improves as the intensity of the ground motion record increases. Full article
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13 pages, 4664 KiB  
Article
Experimental Study on Dynamic Characteristics of Saturated Soft Clay with Sand Interlayer under Unidirectional and Bidirectional Vibration
by Sui Wang, Yuanqiang Cai, Liyong Zhang, Yongjian Pan, Bin Chen, Peng Zhao and Yuanming Fang
Buildings 2023, 13(10), 2534; https://doi.org/10.3390/buildings13102534 - 07 Oct 2023
Viewed by 672
Abstract
The marine and alluvial plains along the southeastern coast of China are widely distributed in sandy formations, including smaller sand lenses and interlayers. The interlayers of sand have a significant impact on the mechanical properties of soft clay. In this paper, a large [...] Read more.
The marine and alluvial plains along the southeastern coast of China are widely distributed in sandy formations, including smaller sand lenses and interlayers. The interlayers of sand have a significant impact on the mechanical properties of soft clay. In this paper, a large number of undrained unidirectional and bidirectional cyclic loading tests for soft clay with sand interlayers were carried out by a dynamic triaxial test system. Test results show that, under unidirectional and bidirectional cyclic vibration, the area of the hysteresis loop decreases and the slope of the connecting line at both ends of the hysteresis loop increases with the increasing of frequency. For the same vibration frequency, the area of the bidirectional vibration hysteresis loop and the slope of the connecting line at both ends are smaller than that of the unidirectional cyclic vibration. Under the same dynamic stress ratio, cumulative axial deformation caused by unidirectional and bidirectional vibration increases with the increasing frequency. Under unidirectional vibration, dynamic elastic modulus decreases at first, and then increases with the increasing frequency. For the same frequency, dynamic elastic modulus of the sample increases with the increase in cycles. Due to the effect of radial cyclic stress, the curves of dynamic elastic modulus and damping ratio with frequency under bidirectional vibration are opposite to those under unidirectional vibration. Full article
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19 pages, 5459 KiB  
Article
Characteristics and Mechanism of Large Deformation of Tunnels in Tertiary Soft Rock: A Case Study
by Dengxue Liu, Shuling Huang, Xiuli Ding, Jianjun Chi and Yuting Zhang
Buildings 2023, 13(9), 2262; https://doi.org/10.3390/buildings13092262 - 06 Sep 2023
Cited by 1 | Viewed by 780
Abstract
During the excavation of a water-conveyance tunnel in Tertiary soft rocks in China, significant deformation of the surrounding rocks and damage to the support were observed. Substantial horizontal deformation, reaching magnitudes of meters, was observed in the right side wall after a certain [...] Read more.
During the excavation of a water-conveyance tunnel in Tertiary soft rocks in China, significant deformation of the surrounding rocks and damage to the support were observed. Substantial horizontal deformation, reaching magnitudes of meters, was observed in the right side wall after a certain period of tunnel excavation. Extensive investigations, including field surveys, monitoring data analysis, laboratory tests, and numerical simulations, were conducted to understand the underlying mechanisms of this large deformation. The section of the tunnel with large deformation consisted of Tertiary sandy mudstone, mudstone interbedded with marl, and glutenite. Laboratory tests and mineral composition analysis revealed that the sandy mudstone and mudstone interbedded with marl exhibited low strength, which was closely related to the water content of the rock specimens. The compressive strength gradually decreased with increasing water content, and when the water content of mudstone interbedded with marl reached 26.96%, the uniaxial compressive strength decreased to only 0.24 MPa. Additionally, sandy mudstone and mudstone interbedded with marl contained a significant amount of hydrophilic minerals, with montmorillonite constituting 30% and 34% of the two rock samples, respectively. The tunnel passed beneath a perennially flowing gully, and a highly permeable glutenite layer was present in the middle of the tunnel. This resulted in groundwater seepage from the inverted arch during excavation, leading to the softening effect on the mudstone interbedded with marl in the lower part of the tunnel. Through numerical simulation and back-analysis techniques, the varying degrees of softening induced by groundwater were quantitatively analyzed in the surrounding rocks on the left and right sides. The study revealed that the large deformation of the tunnel was triggered by two factors: the plastic flow caused by tunnel excavation under the low strength of the surrounding rocks and the softening effect of groundwater. The damage to the support system was primarily attributed to the squeezing and swelling deformation of the surrounding rocks and the non-uniform deformation between different rock layers. Full article
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19 pages, 9782 KiB  
Article
Study on the Seismic Response Characteristics of Shield Tunnels with Different General Segment Assembly Methods and Widths
by Shuaifa Zhang, Zhihua Gao, Sui Wang, Bin Chen and Chaozeng Mao
Buildings 2023, 13(8), 2039; https://doi.org/10.3390/buildings13082039 - 10 Aug 2023
Cited by 1 | Viewed by 652
Abstract
Shield tunnels assembled with general ring segments are widely used in urban areas. Segment assembly methods and widths cause changes in the mechanical properties of the structure and influence the seismic response of shield tunnels. To investigate the influence of the assembly method [...] Read more.
Shield tunnels assembled with general ring segments are widely used in urban areas. Segment assembly methods and widths cause changes in the mechanical properties of the structure and influence the seismic response of shield tunnels. To investigate the influence of the assembly method and width of the general ring segment on the seismic performance of a shield tunnel, a three-dimensional refined soil–structure dynamic interaction finite element model of the shield tunnel was established based on ABAQUS, and the mechanical response and joint deformation of the general ring lining under seismic loads were studied. The simulation results show the following: (i) The overall deformation of the tunnel lining is not significantly affected by the assembly method, and the difference is only 5.24% under a 0.4 g earthquake. (ii) The seismic responses of general ring tunnels with different assembly methods are quite different, and the mechanical properties of the shield tunnel assembled with the straight assembly method are better than those of the shield tunnel assembled with staggered joints, but the deformation of the structure is larger. Under the action of a 0.1 g earthquake, the radial force, circumferential force, and bending moment of the staggered 90° assembly tunnel are respectively reduced by 13.6%, 11.1%, and 17.8% compared with the staggered 45° assembly structure, but the maximum intra-opening deformation increases by 0.19, 0.58, and 2.4 mm, respectively. (iii) The internal force distribution of the bolts is controlled by the deformation of the joint; compared with the CF90 and TF assembled tunnels, the mechanical properties and deformation characteristics of the CF45 and CF90 assembled tunnels are more reasonable. (iv) The extrados and intrados joint opening deformation and shear dislocation of the 1.2 m wide general ring segment under the staggered assembly increase by 1.2 mm and 1.03 mm, respectively, compared with the 1.5 m wide segment, while the radial force, circumferential force, and bending moment are reduced by 24.4%, 36.5%, and 41.7%, respectively, indicating that the seismic performance of the shield tunnel with a segment width of 1.5 m is better than that of the shield tunnel with a width of 1.2 m. Full article
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23 pages, 8544 KiB  
Article
Estimation Method for an In Situ Stress Field along a Super-Long and Deep-Buried Tunnel and Its Application
by Qitao Pei, Xiaonan Wang, Lihong He, Lu Liu, Yong Tian and Cai Wu
Buildings 2023, 13(8), 1924; https://doi.org/10.3390/buildings13081924 - 28 Jul 2023
Viewed by 773
Abstract
Aiming at some stress-induced failure phenomena in surrounding rock that occur during the construction of super-long and deep-buried tunnels, a method for estimating the in situ stress in the tunnels based on multivariate information integration is proposed, which uses a small amount of [...] Read more.
Aiming at some stress-induced failure phenomena in surrounding rock that occur during the construction of super-long and deep-buried tunnels, a method for estimating the in situ stress in the tunnels based on multivariate information integration is proposed, which uses a small amount of in situ stress measurement, stereographic projection technology, and a numerical simulation method. Firstly, by conducting a macroscopic analysis of the regional geological structure, topography, and pre-excavated small tunnels (such as exploration of adits and pilot tunnels), the strength of the tectonic stress field and the orientation of the principal stresses in the tunnel sections are preliminarily determined. Secondly, the reliability of the in situ stress measurement data were analyzed using full-space stereographic projection and the plane stress projection method. Then, some representative measurement points that reflected the distribution characteristics of in situ stress in the project area, on the whole, were determined. Thirdly, the finite difference (FDM) and multiple regression analysis (MRA) methods were used to inverse the in situ stress field in the project area. The proposed method was applied to a super-long and deep-buried tunnel project in Qinling, and the in situ stress distribution characteristics of the tunnel sections at different mileages were obtained. The results show that both the calculated principal stress values and the azimuth angle of the maximum horizontal principal stress are in good agreement with the measured ones, indicating that the method used in this study is reasonable. Finally, the typical surrounding rock failure phenomena encountered during the excavation of the project were investigated, and targeted treatment measures were proposed. The research results can provide references for support design and disaster management of surrounding rock in deep-buried long tunnels. Full article
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20 pages, 12220 KiB  
Article
Experimental Study on Mechanical Properties of Structured Clay under Different Unloading Rates and Unloading Stress Paths
by Lu Li, Meng Zang, Rongtang Zhang and Haijun Lu
Buildings 2023, 13(6), 1544; https://doi.org/10.3390/buildings13061544 - 17 Jun 2023
Cited by 1 | Viewed by 838
Abstract
Consolidated undrained triaxial shear tests were performed on undisturbed saturated structured clay at three unloading rates (0.1, 0.25, and 2.5 kPa/min) using a GDS triaxial system to determine the effects of different unloading rates and unloading stress paths on the stress–strain relationship, pore [...] Read more.
Consolidated undrained triaxial shear tests were performed on undisturbed saturated structured clay at three unloading rates (0.1, 0.25, and 2.5 kPa/min) using a GDS triaxial system to determine the effects of different unloading rates and unloading stress paths on the stress–strain relationship, pore pressure variation, and failure strength characteristics of Zhanjiang structured clay. Microstructural changes in the clay were observed during shear tests at different unloading rates. Furthermore, the obtained stress–strain relationship indicates strain-softening under different unloading stress paths. Under the same axial strain, a larger unloading rate caused a larger deviatoric stress. Under the same conditions, the higher the confining pressure, the greater the peak pore pressure, the smaller the unloading rate, the greater the pore pressure development, and the greater the variation in the pore pressure. Moreover, the undrained shear strength increased with an increase in the unloading rate from 0.1 to 2.5 kPa/min. The change in the unloading rate had a greater effect on the undrained strength under the passive tensile path than that under the passive compression path. The microstructure of the Zhanjiang structured clay changed after shear tests at different unloading rates, exhibiting various degrees of adjustment in the particle arrangement, contact relations, pore sizes, and shapes. Full article
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16 pages, 4364 KiB  
Article
Research on Dynamic Pile-Driving Formula Parameters and Driving Feasibility of Extra-Long PHC Pipe Piles
by Xiaomin Liu, Yonggang Xiao, Junlong Zhou, Longbo Ge and Ziwen Song
Buildings 2023, 13(5), 1302; https://doi.org/10.3390/buildings13051302 - 16 May 2023
Viewed by 1603
Abstract
Prestressed high-strength concrete (PHC) pipe pile has the advantages of high single pile bearing capacity, a wide range of applications, good driving resistance, fast construction speed, etc. It has been widely used in high-rise buildings, bridges, ports, and other industries. The application of [...] Read more.
Prestressed high-strength concrete (PHC) pipe pile has the advantages of high single pile bearing capacity, a wide range of applications, good driving resistance, fast construction speed, etc. It has been widely used in high-rise buildings, bridges, ports, and other industries. The application of extra-long PHC pipe piles with a length of more than 50 m is increasing. However, there are few studies on the drivability and hammering criteria of extra-long PHC piles. To analyze the drivability of extra-long piles and predict their bearing capacity, in this paper, high-strain dynamic tests were carried out on 14 test sections with the pile foundation of Temburong Bridge in Brunei as the research background. The hammer stop control criteria calculated according to the Hiley formula would lead to excessive hammering. Three types of damage occurred during construction: pile shaft breakage, weld tearing, and pile head breakage. The weight and drop height of the piling hammer selected for this project were appropriate, and the extra-long test piles can be hammered to the design depth. The values of Cp (Compression of the pile) and n (the efficiency of the blow) were fitted based on the dynamic test data, which provided a more accurate reference for the selection of subsequent piling parameters of the project. It provides a more accurate calculation method for predicting the bearing capacity of extra-long PHC piles and provides control criteria for pile stopping and a scientific basis for their design and construction. Full article
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14 pages, 2745 KiB  
Article
Mechanical Behavior of Fully Grouted Rock Bolts in Hydraulic Tunnels Subjected to Elevated Ground Temperatures
by Haibo Jiang, Shuangxi Li, Qinglin Li and Juncai Xu
Buildings 2023, 13(5), 1280; https://doi.org/10.3390/buildings13051280 - 14 May 2023
Viewed by 1030
Abstract
In this study, the mechanical behavior of fully grouted rock bolts in hydraulic tunnels subjected to elevated ground temperatures was investigated. A differential equation for axial displacement of the rock bolt was formulated, which considers the force equilibrium of infinitesimal bolt segments and [...] Read more.
In this study, the mechanical behavior of fully grouted rock bolts in hydraulic tunnels subjected to elevated ground temperatures was investigated. A differential equation for axial displacement of the rock bolt was formulated, which considers the force equilibrium of infinitesimal bolt segments and the stress transfer mechanism at the anchor–rock interface. The distribution functions for axial stress within the bolt and the interfacial shear stress were obtained by solving the differential equation, which incorporated the displacement of the surrounding rock mass as a parameter. This study showed that the effectiveness of the bolt–shotcrete support system decreases over time, considering the displacement relaxation rate of the surrounding rock mass. The mechanical model’s variation laws at 20 °C, 50 °C, and 80 °C were summarized by integrating the thermal deformation equation for material parameters, and the numerical simulation results were compared and analyzed. The findings revealed that the bond strength between the rock bolt and the rock mass diminishes as the temperature of the surrounding rock increases, leading to a reduction of interfacial shear stress at both extremities of the bolt. Moreover, the maximum axial force within the bolt escalates as the neutral point migrates farther from the tunnel wall. Full article
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22 pages, 7708 KiB  
Article
3-D Numerical Simulation of Seismic Response of the Induced Joint of a Subway Station
by Dengzhou Quan, Shaobo Chai, Yuling Wang, Zhishuang Fan and Yonghong Bu
Buildings 2023, 13(5), 1244; https://doi.org/10.3390/buildings13051244 - 09 May 2023
Cited by 2 | Viewed by 866
Abstract
In recent times, induced joints have been set along the length of subway stations in order to avoid disordered cracking of the main structures occurring due to temperature stress, concrete shrinkage, creep, or uneven foundation settlement. At present, the use of induced joints [...] Read more.
In recent times, induced joints have been set along the length of subway stations in order to avoid disordered cracking of the main structures occurring due to temperature stress, concrete shrinkage, creep, or uneven foundation settlement. At present, the use of induced joints in subway station structures is mainly based on engineering experience. The seismic response of induced joints has not yet been well explained, much less mastered. In this study, a 3-D numerical model of a subway station incorporating certain sorts of induced joints is established systematically. Then, the seismic response of those induced joints applied in different positions and various forms has been studied under different seismic waves by varying the spectral characteristics and peak acceleration values of the waves. The results show that the horizontal relative sliding displacement of the structures on both sides of an induced joint increases gradually from bottom to top along the structure of the subway station. While the vertical sliding displacements that occur along the section width are larger at both ends of the induced joints than in the middle. What is more, with an increase in seismic intensity, the horizontal relative sliding displacement becomes larger, while the vertical displacement becomes even smaller. In addition, the relative sliding displacement can be reduced by increasing the residual longitudinal reinforcement ratio of the induced joint. Furthermore, it is discovered that the setting of key grooves at the bottom plate of the induced joint section has a certain effect on controlling the horizontal relative sliding displacement, as well as a significant effect on preventing the vertical relative dislocation of the structures on both sides of the induced joint. Full article
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