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15 pages, 10807 KiB

Open AccessArticle

Numerical Investigation of Stratified Slope Failure Containing Rough Non-Persistent Joints Based on Distinct Element Method

by Yishan Zhang, Yilin Fu, Ran Qin and Peitao Wang

Appl. Sci. 2024, 14(9), 3665; https://doi.org/10.3390/app14093665 - 25 Apr 2024

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Abstract

To address the critical issue of slope stability in jointed rock masses with complex and rough structural planes, a rough joint network model using the Fourier transform was proposed and applied to the Shilu open pit mine. The on-site structural plane survey results [...] Read more.

To address the critical issue of slope stability in jointed rock masses with complex and rough structural planes, a rough joint network model using the Fourier transform was proposed and applied to the Shilu open pit mine. The on-site structural plane survey results were combined with MATLAB and PFC2D to establish numerical models for slope stability analysis considering both linear-jointed and rough-jointed rock slopes. By comparing the slip body and fracture distribution, it was found that the rough-jointed slope was stabler than the linear-jointed slope. In addition, the fracture patterns and slip displacement were significantly influenced by the inclination and undulation of the bedding planes. Slip failure patterns occurred when the angle of inclination was set at 60°. The joints played a crucial role in inducing the shear strength of slope rock masses, and the slide area was mainly observed in the shallow slope surface for inclination angles of 0° and 45°, and in the middle deep area for 60° and 90°. These results demonstrated the importance of considering rough non-persistent fractures when developing a new numerical model for slope failure modes. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

16 pages, 6269 KiB

Open AccessArticle

Practical Considerations in the Design of Passive Free Piles in Sliding Soil

by Paolo Carrubba and Claudia Pergola

Appl. Sci. 2024, 14(8), 3334; https://doi.org/10.3390/app14083334 - 15 Apr 2024

Viewed by 358

Abstract

The stabilisation of shallow translational landslides can be carried out by using large diameter concrete piles, with the aim of increasing the available strength along the slip surface. In the following article, 3D numerical models of a free-head flexible pile embedded into a [...] Read more.

The stabilisation of shallow translational landslides can be carried out by using large diameter concrete piles, with the aim of increasing the available strength along the slip surface. In the following article, 3D numerical models of a free-head flexible pile embedded into a translational type of landslide are studied. The landslide model has a given inclination angle, β, and a thickness, D, while the reinforced concrete pile has a fixed diameter, d, and a length, D + L, in the perspective of studying the failure modes B1, BY and B2 of free-head flexible piles. In this category of piles, collapse is reached with the formation of plastic hinges. Both the soil and the concrete are modelled with simple constitutive models, such as Mohr–Coulomb for soil and the elastic-perfectly plastic for the concrete pile, in order to carry out the design approaches provided by Eurocode, as well as to highlight some practical aspects of soil–structure interaction during the landslide displacements. The results highlight how the achievement of the shear strength in a flexible free-head concrete pile generally precedes the achievement of the ultimate bending moment associated with the development of plastic hinges. Furthermore, the axial load supported by the pile may itself contribute to the overall strength available along the slip surface. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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18 pages, 4337 KiB

Open AccessArticle

Stability Analysis of Three-Dimensional Tunnel Face Considering Linear and Nonlinear Strength in Unsaturated Soil

by Yushan Yang, Hong Liao and Jianqun Zhu

Appl. Sci. 2024, 14(5), 2080; https://doi.org/10.3390/app14052080 - 01 Mar 2024

Viewed by 394

Abstract

The shear strength of unsaturated soils exhibits significant nonlinearity, while previous studies often simplified it with linear strength models. The objective of this paper is to investigate the distinctions in the stability of three-dimensional (3D) tunnel faces when using linear and nonlinear strength [...] Read more.

The shear strength of unsaturated soils exhibits significant nonlinearity, while previous studies often simplified it with linear strength models. The objective of this paper is to investigate the distinctions in the stability of three-dimensional (3D) tunnel faces when using linear and nonlinear strength models. A new 3D rotational failure mechanism and an extended form of the Mohr–Coulomb (M-C) failure criterion were integrated into the kinematically limited analysis (KLA) framework to describe the failure characteristics of tunnel faces. Subsequently, the factor of safety (FS) of the 3D tunnel faces was calculated using the strength reduction method (SRM). In the discussion section, the impacts of nonlinear shear strength, matric suction in the unsaturated soils, and the 3D geometric parameters of the tunnel on the stability of the tunnel face were analyzed. The outcomes indicate that, in unsaturated soil conditions, diverse nonlinear strength calculation models and soil types exert disparate influences on the FS of 3D tunnel faces. The main novelty of this study lies in establishing an effective method for assessing the stability of tunnel faces in unsaturated soils. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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21 pages, 7290 KiB

Open AccessArticle

Physical and Numerical Models of Mechanically Stabilized Earth Walls Using Self-Fabricated Steel Reinforcement Grids Applied to Cohesive Soil in Vietnam

by Truong-Linh Chau, Thu-Ha Nguyen and Van-Ngoc Pham

Appl. Sci. 2024, 14(3), 1283; https://doi.org/10.3390/app14031283 - 03 Feb 2024

Viewed by 737

Abstract

Mechanically stabilized earth (MSE) walls have been widely applied in construction to maintain the stability of high embankments. In Vietnam, imported reinforcement materials are expensive; thus, finding locally available materials for MSE walls is beneficial. This study examines the behavior of an MSE [...] Read more.

Mechanically stabilized earth (MSE) walls have been widely applied in construction to maintain the stability of high embankments. In Vietnam, imported reinforcement materials are expensive; thus, finding locally available materials for MSE walls is beneficial. This study examines the behavior of an MSE wall using local reinforcement materials in Danang, Vietnam. The MSE was reinforced by self-fabricated galvanized steel grids using CB300V steel with 3 cm ribs. The backfill soil was sandy clay soil from the local area with a low cohesion. A full-scale model with full instrumentation was installed to investigate the distribution of tensile forces along the reinforcement layers. The highest load that caused the wall to collapse due to internal instability (reinforcement rupture) was 302 kN/m², which is 15 times greater than the design load of 20 kN/m². The failure surface within the reinforced soil had a parabolic sliding shape that was similar to the theoretical studies. At the failure load level, the maximum lateral displacement at the top of the wall facing was small (3.9 mm), significantly lower than the allowable displacement for a retaining wall. Furthermore, a numerical model using FLAC software 7.0 was applied to simulate the performance of the MSE wall. The modeling results were in good agreement with the physical model. Thus, self-fabricated galvanized steel grids could confidently be used in combination with the local backfill soil for MSE walls. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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25 pages, 9688 KiB

Open AccessArticle

Study of Load Calculation Models for Anti-Sliding Short Piles Using Finite Difference Method

by Xunchang Li, Yutong Ran, Kang Wang and Zhengzheng Shi

Appl. Sci. 2023, 13(22), 12399; https://doi.org/10.3390/app132212399 - 16 Nov 2023

Viewed by 580

Abstract

Anti-sliding short piles, a novel technique for slope stabilization, have been applied in engineering practices. Nonetheless, a mature structural calculation theory for these piles is still lacking. In this paper, the study presents an internal force solution model for anti-sliding short piles using [...] Read more.

Anti-sliding short piles, a novel technique for slope stabilization, have been applied in engineering practices. Nonetheless, a mature structural calculation theory for these piles is still lacking. In this paper, the study presents an internal force solution model for anti-sliding short piles using the finite difference method. By extending the Euler–Bernoulli beam theory and defining boundary conditions, this study develops a set of finite difference equations for computing the structural forces of anti-sliding short piles. Furthermore, this study conducted laboratory model tests on soil landslide cases reinforced with anti-sliding short piles. By comparing the internal forces and deformations of these piles, the test validates the proposed calculation model for anti-sliding short piles. The results suggest that treating the load-bearing and embedded sections as a unified entity during the calculation process, instead of applying continuity conditions separately at the sliding surface as performed in traditional methods, simplifies the complex solving procedure. Moreover, under identical loading conditions, the displacement, bending moment, and shear force data obtained through the finite difference method closely coincide with the measurements from the model tests, confirming the reliability of the anti-sliding short pile calculation model. Additionally, this study demonstrates that reducing the spacing between nodes along the entire anti-sliding short pile, i.e., decreasing the value of the differential segment length ‘h’, results in more precise computational outcomes. This research offers valuable insights and references for sustainable solutions in the realm of geological disaster prevention and control. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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13 pages, 3382 KiB

Open AccessArticle

Application of the Improved Entry and Exit Method in Slope Reliability Analysis

by Rong Yang, Boyan Sun, Yukuai Wan and Xinyue Gao

Appl. Sci. 2023, 13(18), 10081; https://doi.org/10.3390/app131810081 - 07 Sep 2023

Viewed by 1036

Abstract

The entry and exit method is a simple and practical method to decide the critical slip surface of slope. Nevertheless, it has the drawback of sacrificing computational efficiency to improve search accuracy. To solve this problem, this paper proposes an improved entry and [...] Read more.

The entry and exit method is a simple and practical method to decide the critical slip surface of slope. Nevertheless, it has the drawback of sacrificing computational efficiency to improve search accuracy. To solve this problem, this paper proposes an improved entry and exit approach to search for the critical slip surface. On basis of the random fields produced by applying the Karhunen–Loève expansion approach, the simplified Bishop’s method combined with the improved entry and exit method is used to decide the critical slip surface and its relevant minimum factor of security. Then, the failure probability is calculated by conducting Monte Carlo simulation. Two instances are reanalyzed to validate the precision and efficiency of the method. Meaningful comparisons are made to show the calculating precision and calculating efficiency of the improved entry and exit method in searching for the minimum security factor of slope, based on which the effect of the reduced searching range on slope reliability was explored. The outcomes suggest that the approach offers a practical device for assessing the reliability of slopes in spatially variable soils. It can significantly enhance the computational efficiency in relatively high-computational precision of slope reliability analysis. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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18 pages, 2443 KiB

Open AccessArticle

Prediction of Seismic Bearing Capacity Considering Nonlinearity and Dilatancy by Sequential Quadratic Programming

by Hong Liao and De Zhou

Appl. Sci. 2023, 13(5), 3215; https://doi.org/10.3390/app13053215 - 02 Mar 2023

Viewed by 1104

Abstract

Most of the published literature regarding bearing capacity are often focused on linear and associative soils. Concerning the intrinsic strength nonlinearity in dilatancy soils, this study investigates the problem of the seismic bearing capacity in the framework of the kinematic theorem of limit [...] Read more.

Most of the published literature regarding bearing capacity are often focused on linear and associative soils. Concerning the intrinsic strength nonlinearity in dilatancy soils, this study investigates the problem of the seismic bearing capacity in the framework of the kinematic theorem of limit analysis. The conventional linear Mohr–Coulomb criterion is substituted with a nonlinear power law criterion to depict the nonlinearity of the soil strength. The non-associative feature of soil materials is considered by defining a nonlinear dilatancy coefficient. A generalized tangential technique is accordingly introduced to linearize the strength envelope for making the nonlinear criterion tractable in the analysis. A non-symmetrical translational failure mechanism that is comprised of several rigid wedges is used to characterize the failure of the foundation at the limit state. Moreover, the seismic action is considered by the classic pseudo-static method. Based upon the energy equilibrium theory of the upper-bound limit analysis, new analytical solutions are derived from the work-balanced equation with nonlinearity and dilatancy. This rigorous upper-bound solution is formulated as a multivariate optimization problem and is readily addressed by sequential quadratic programming (SQP). To verify the reliability of the new expressions, the present results are compared with already posted solutions and the original pseudo-dynamic solutions. The comparative results show a good agreement with previous works, and the correctness and rationality of the new analytical solutions are validated. The detailed parametric study reveals that, in the non-associative flow soils, the ultimate bearing capacity is significantly decreased with a reduction in the dilatancy coefficient. Particularly in the linear condition, namely m = 1, the larger the internal friction angle is, the more obvious the influence of the non-associative feature on the bearing capacity is. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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16 pages, 9941 KiB

Open AccessArticle

Field Pull-Out Tests of Percussion Driven Earth Anchors (PDEAs)

by Natnael Tilahun Asfaw, Gang Lei, Mehran Azizian, Arjan Poudel, Laureano Hoyos and Xinbao Yu

Appl. Sci. 2023, 13(4), 2132; https://doi.org/10.3390/app13042132 - 07 Feb 2023

Viewed by 1582

Abstract

Percussion driven earth anchors (PDEAs) are driven into soils using an installation steel hammer rod. PDEAs are relatively easy to install and have gained wide applications recently. The Texas Department of Transportation (TxDOT) planned to use these anchors for slope stability mitigation along [...] Read more.

Percussion driven earth anchors (PDEAs) are driven into soils using an installation steel hammer rod. PDEAs are relatively easy to install and have gained wide applications recently. The Texas Department of Transportation (TxDOT) planned to use these anchors for slope stability mitigation along the Clear Fork Trinity River at Interstate Highway 20 (IH-20) in Benbrook, Texas. However, there are no straightforward design and construction guidelines for these systems. In addition, the pull-out capacity and failure mechanisms of PDEAs in clayey soils have not been thoroughly studied. In this study, three PDEAs, Duckbill model 138 II (DB-138 II), were installed and tested on the proposed west channel bank slope to acquire the ultimate pull-out capacity. The anchors were embedded to an average depth of 10 feet into the slope bank, predominantly consisting of sandy lean clay (CL) soil. The slope was graded at an average 2:1 to 2.5:1 configuration. After installation, the anchors were subjected to an upward pull-out force using a hydraulic jack system to measure their pull-out capacity. The pull-out load, displacement, and strains were continuously recorded with a load cell, a linear variable differential transformer (LVDT), and a strain gauge, respectively. Pull-out load versus displacement curves were produced and analyzed to determine the behavior of the anchors. An empirical estimation method was then chosen to estimate pull-out capacity based on undrained shear strengths obtained either from laboratory tests or in situ Texas cone penetration (TCP) data. The comparison between estimated and field-obtained pull-out capacities showed that the pull capacity estimated using TCP data resulted in reasonably good agreement with the field-obtained capacity. The field experiment results help us to understand the relationship between the calculated and actual field pull-out resistance when PDEAs are used in clayey soil slopes. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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13 pages, 6014 KiB

Open AccessArticle

Model Test Study of the Synergistic Interaction between New and Existing Components of Sheet Pile Walls

by Wenhui Zhao, Xiaomin Wu and Xuening Ma

Appl. Sci. 2023, 13(3), 1557; https://doi.org/10.3390/app13031557 - 25 Jan 2023

Viewed by 1164

Abstract

New and existing components of retaining structures are often combined in the width section. When combining the design and use requirements of the existing and new structures, the synergistic interactions between the existing and new structures and the design and working conditions require [...] Read more.

New and existing components of retaining structures are often combined in the width section. When combining the design and use requirements of the existing and new structures, the synergistic interactions between the existing and new structures and the design and working conditions require clarification. In conjunction with an actual project, a sheet pile wall consisting of existing and new components is proposed to retain an embankment. Indoor model tests were carried out to simulate the excavation and compaction and investigate changes in earth pressure, pile bending moment, shear force, and load-sharing ratio of the new and existing sheet pile walls at different stages. The results show that the earth pressure of the cantilever section of the existing and new piles increases with an increase in the fill volume or the upper uniform load. An inflection point is observed in the earth pressure curve halfway between the pile top and the ground due to sudden changes in the pile and soil stiffness. The bending moment of the new and existing piles increases and decreases with the distance from the top of the pile under different working conditions, and the maximum bending moment occurred at 0.485 and 0.9 m from the bottom of the existing pile and the bottom of the new pile, respectively. The lateral displacement of the new and existing piles decreases with the distance from the top of the pile. Due to the adjustment of the structural force in the cantilever section and the soil reaction force in front of the pile, the displacement curves of the new and existing piles are similar in the cantilever section. The displacement in the anchored section is initially larger for the existing pile than for the new pile but then becomes similar for both piles. In working condition 5, the top displacement of the existing pile was 6.531 mm, exceeding the control value (5.6 mm). The earth-pressure-sharing ratio of the existing pile decreases with an increase in the width of the filling material or the load. When the load was applied, the earth-pressure-sharing ratio of the existing pile was 0.451, indicating that the structural design of the combined sheet pile wall is reasonable. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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17 pages, 5403 KiB

Open AccessArticle

Probabilistic Risk Assessment of Soil Slope Stability Subjected to Water Drawdown by Finite Element Limit Analysis

by Xiaobing Wang, Xiaozhou Xia, Xue Zhang, Xin Gu and Qing Zhang

Appl. Sci. 2022, 12(20), 10282; https://doi.org/10.3390/app122010282 - 12 Oct 2022

Cited by 5 | Viewed by 1436

Abstract

This study investigates the probabilistic stability of embankment slopes subjected to water level drawdown using the random field finite element method (RFEM) with strength reduction technology. The shear strength of soil properties was controlled by cohesion and internal friction angle for the slope [...] Read more.

This study investigates the probabilistic stability of embankment slopes subjected to water level drawdown using the random field finite element method (RFEM) with strength reduction technology. The shear strength of soil properties was controlled by cohesion and internal friction angle for the slope shear failure. The cohesion and internal friction angle were modeled by a random field following the log-normal distribution. The factor of safety (FOS) for the embankment slope with random soil is calculated by strength reduction technology. During the numerical simulation, the limit analysis upper bound and lower bound method are applied to the finite element method, respectively, to obtain the upper bound and lower bound value of the FOS. Seepage action is also considered during the water drawdown by setting five different water levels (WLs). A total of 1000 Monte Carlo simulations are performed for each work condition, resulting in histograms of the FOSs. The results show that the FOSs obtained by the random field model are all lower than those by the deterministic method. Even if the FOSs obtained by the two methods are close, there still exists the possibility of slope failure. Compared to the deterministic results, the RFEM method is more reasonable for evaluating slope stability. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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18 pages, 5970 KiB

Open AccessArticle

Experimental Study on Failure Mechanism and Mode of Fly-Ash Dam Slope Triggered by Rainfall Infiltration

by Hong-Kai Niu, Qiang Li, Li-Ting Zhang, Xin Li and Jun-Tao Wang

Appl. Sci. 2022, 12(19), 9404; https://doi.org/10.3390/app12199404 - 20 Sep 2022

Cited by 2 | Viewed by 1358

Abstract

The fly-ash dam is used to store the fly ash discharged from the thermal power plant. A fly-ash dam is a special slope built with fly ash, and rainfall infiltration is an important reason to induce the landslide of this kind of slope. [...] Read more.

The fly-ash dam is used to store the fly ash discharged from the thermal power plant. A fly-ash dam is a special slope built with fly ash, and rainfall infiltration is an important reason to induce the landslide of this kind of slope. In this paper, the laboratory tests of different slope ratios and initial seepage fields under rainfall were carried out, aimed at studying the failure mechanism, failure mode, triggering mechanism, and influence factors for the slope instability of the fly ash dam slope under rainfall infiltration. The results show that: (I) Three failure mechanisms were found in the tests: sliding failure, runoff erosion, and flow-slide failure. Due to the low density of fly ash, runoff erosion is more likely to occur under rainfall. Differently from clay slope, flow slide is an important failure mechanism of fly ash slope under rainfall. (II) Local erosion damages caused by runoff erosion and flow slide are the important triggering factors of the fly-ash dam slope failure under rainfall. (III) Three failure modes were observed in the test: the overall sliding failure of the slope, the retrogressive landslide caused by multi-stage local sliding, and the gradual erosion failure of the slope (caused by the combined action of runoff erosion and flow slide). (IV) The slope ratio has an important influence on the failure mode. With the decrease in slope ratio, the failure mode evolves from sliding failure to flow-slide failure and runoff erosion failure. The greater the slope ratio, the more obvious the sliding failure characteristics; the lower the slope rate, the greater the runoff erosion damage. The existence of an internal seepage field in the slope intensifies the occurrence of flow slide. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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18 pages, 9715 KiB

Open AccessArticle

Determination of Landslide Displacement Warning Thresholds by Applying DBA-LSTM and Numerical Simulation Algorithms

by Yue Dai, Wujiao Dai, Wenkun Yu and Dongxin Bai

Appl. Sci. 2022, 12(13), 6690; https://doi.org/10.3390/app12136690 - 01 Jul 2022

Cited by 6 | Viewed by 1426

Abstract

Numerical simulation has emerged as a powerful technique for landslide failure mechanism analysis and accurate stability assessment. However, due to the bias of simplified numerical models and the uncertainty of geomechanical parameters, simulation results often differ greatly from the actual situation. Therefore, in [...] Read more.

Numerical simulation has emerged as a powerful technique for landslide failure mechanism analysis and accurate stability assessment. However, due to the bias of simplified numerical models and the uncertainty of geomechanical parameters, simulation results often differ greatly from the actual situation. Therefore, in order to ensure the accuracy and rationality of numerical simulation results, and to improve landslide hazard warning capability, techniques and methods such as displacement back-analysis, machine learning, and numerical simulation are combined to create a novel landslide warning method based on DBA-LSTM (displacement back-analysis based on long short-term memory networks), and a numerical simulation algorithm is proposed, i.e., the DBA-LSTM algorithm is used to invert the equivalent physical and mechanical parameters of the numerical model, and the modified numerical model is used for stability analysis and failure simulation. Taking the Shangtan landslide as an example, the deformation mechanism of the landslide was analyzed based on the field monitoring data, and subsequently, the superiority of the DBA-LSTM algorithm was verified by comparing it with DBA-BPNN (displacement back-analysis based on back-propagation neural network); finally, the stability of the landslide was analyzed and evaluated a posteriori using the warning threshold calculated by the proposed method. The analytical results show that the displacement back-analysis based on the machine learning (DBA-ML) algorithm can achieve more than 95% accuracy, and the deep learning algorithm exemplified by LSTM had higher accuracy compared to the classical BPNN algorithm, meaning that it can be used to further improve the existing intelligent inversion theory and method. The proposed method calculates the landslide’s factor of safety (FOS) before the accelerated deformation to be 1.38 and predicts that the landslide is in a metastable state after accelerated deformation rather than in failure. Compared to traditional empirical warning models, our method can avoid false warnings and can provide a new reference for research on landslide hazard warnings. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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18 pages, 4123 KiB

Open AccessArticle

Seismic Stability for 3D Two-Step Slope Governed by Non-Linearity in Soils Using Modified Pseudo-Dynamic Approach

by Yushan Yang and De Zhou

Appl. Sci. 2022, 12(13), 6482; https://doi.org/10.3390/app12136482 - 26 Jun 2022

Cited by 3 | Viewed by 1404

Abstract

Seismic events are an active factor in causing slope instability, and the existing pseudo-dynamic method ignores some practical engineering conditions. In this paper, the seismic stability of three-dimensional (3D) two-step slopes is evaluated utilizing the modified pseudo-dynamic method based on the kinematical approach [...] Read more.

Seismic events are an active factor in causing slope instability, and the existing pseudo-dynamic method ignores some practical engineering conditions. In this paper, the seismic stability of three-dimensional (3D) two-step slopes is evaluated utilizing the modified pseudo-dynamic method based on the kinematical approach of limit analysis, in which the nonlinear characteristics of soil are considered using the generalized tangent technique. A 3D horn-like rotational failure mechanism is established to solve internal energy dissipation and external force work, in which the seismic work is considered in addition to the soil weight work and obtained by the layer-wise summation method. Based on the force-increase technique, the analytical expression for the safety factor (FS) of 3D two-step slopes is derived more readily. To verify the reliability of the new expression, the present results are compared with already posted solutions and the original pseudo-dynamic solutions. Ultimately, the sensitivity discussions are carried out to investigate the impacts of various factors on slope stability. This has some significance for the design and safety of 3D two-step slopes. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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19 pages, 6329 KiB

Open AccessArticle

Dynamic Response of a Heavy-Haul Railway Tunnel’s Bottom Structures in Hard Rock

by Cong Liu, Qianlong Tang, Bo Wu, Qiang Wan and Yisheng Ye

Appl. Sci. 2022, 12(11), 5721; https://doi.org/10.3390/app12115721 - 04 Jun 2022

Cited by 1 | Viewed by 1821

Abstract

A train–tunnel–surrounding rock numerical model was established by using ABAQUS to analyze the dynamic response of a heavy-haul railway tunnel in hard rock, quantify the influence of the train axle load on the tunnel dynamic response and determine its potential vulnerable position. The [...] Read more.

A train–tunnel–surrounding rock numerical model was established by using ABAQUS to analyze the dynamic response of a heavy-haul railway tunnel in hard rock, quantify the influence of the train axle load on the tunnel dynamic response and determine its potential vulnerable position. The results suggested that: Under the 30 t train load and surrounding rock pressure coupling, the maximum principal stress caused by rock pressure was 1.27 MPa, located at the bottom of the structure below the side drain; the maximum dynamic response of the tunnel structure and base rock was located directly below the rail. The lower part of the side drain and rail was the vulnerable position in the tunnel bottom structure, and the probability of base disease under the rail may be higher than that in soft-rock tunnels, for it has a greater dynamic response and thinner structure compared to a soft-rock tunnel. The maximum principal stress amplitude of the tunnel structure and base rock were 129.3 kPa and 43.0 kPa, respectively. When the axle load increased by 1 t, the dynamic amplitude of the structure’s maximum principal stress increased by about 4.14 kPa, and the base rock’s maximum principal stress increased by about 1.33 kPa. The rock pressure was not negligible in the dynamic analysis of the railway tunnel, and the dynamic response of the tunnel bottom structure and base rock will decrease, obviously, when the rock pressure is ignored. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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16 pages, 4838 KiB

Open AccessArticle

The Changsha Historic Urban Area: A Study on the Changing Accessibility of the Road Network

by Jinyu Fan, Bohong Zheng, Qianlong Tang, Boyang Zhang and Ning Liu

Appl. Sci. 2022, 12(6), 2796; https://doi.org/10.3390/app12062796 - 09 Mar 2022

Cited by 7 | Viewed by 1762

Abstract

In this study, we used a complex network analysis to examine the accessibility features of changing road networks in historic urban areas. We aimed to discover the pattern of evolution after studying the accessibility of the road network in the Changsha historic urban [...] Read more.

In this study, we used a complex network analysis to examine the accessibility features of changing road networks in historic urban areas. We aimed to discover the pattern of evolution after studying the accessibility of the road network in the Changsha historic urban area over four periods of time. The results were as follows: the layout of the urban road network shows repetitive cluster–parent–subsidiary development, which provides evidence of adaptive adjustment in urban road development; vulnerability has been kept low in the changing urban road network, while the spatial framework of the Changsha historic center is fixed; the evolving urban road network generally shows a deteriorating level of stability, which is largely affected by the shape of the network; the degree centrality (1877, 1.87%; 1917, 1.32%; 1987, 1.85%; 2021, 1.51%) of the urban road network shows a decreasing trend, meaning that the network is generally becoming more balanced in its evolution; and the accessibility of land plots currently used to preserve cultural relics and historic sites remains at a medium to low level, and improvements are needed for some plots. In analyzing the changing accessibility of urban roads in the historic center of Changsha city, two major problems for road renewal were identified: (1) unbalanced development of the urban space due to capital-based projects and (2) providing an appropriate increase in plot accessibility while putting equal emphasis on the protection of the spatial framework in the historic urban area. We conclude that a dynamic review of urban road network accessibility and its targeted optimization are of great significance for the protection and development of Changsha’s historic urban area. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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16 pages, 12405 KiB

Open AccessPerspective

Study on the Stability of Soil–Rock Mixture Slopes Based on the Material Point Strength Reduction Method

by Zaixian Xu, Chao Li, Fang Fang and Fufei Wu

Appl. Sci. 2022, 12(22), 11595; https://doi.org/10.3390/app122211595 - 15 Nov 2022

Cited by 3 | Viewed by 1197

Abstract

In this paper, the material point strength reduction method is used to investigate the stability of soil–rock mixture (SRM) slopes and the whole process of large deformation occurring after destabilization. A comparative study with homogeneous soil slopes is conducted. First, a material point [...] Read more.

In this paper, the material point strength reduction method is used to investigate the stability of soil–rock mixture (SRM) slopes and the whole process of large deformation occurring after destabilization. A comparative study with homogeneous soil slopes is conducted. First, a material point slope model with typical shapes, a homogeneous soil slope, and an SRM slope with stones of different sizes distributed inside is established. Next, gravity is linearly added to establish the initial state of the slopes. Then the material strength of the slope is discounted according to the criterion of strength discounting. The material point method (MPM) simulations of the two slopes are carried out separately until the slope’s displacement changes abruptly to determine the slope’s safety factor. The final accumulation form of the slope after the damage is studied. Finally, the deformation characteristics of the two slopes under extreme conditions are explored. The research shows that the stones are beneficial to the slope in maintaining slope stability, and due to the presence of stones, the slope presents different characteristics from the pure soil slope when damage occurs. Full article

(This article belongs to the Special Issue Slope Stability and Earth Retaining Structures)

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