Slip Surface Research Articles

Investigation of the Disintegration Characteristics of Neogene Mudstone at Different Burial Depths

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.

Theoretical solutions for the anchoring force of 3‐D anchored slope and optimization strategy for anchoring force distribution

AbstractBased on the three‐dimensional limit equilibrium method with modifying normal stress over the slip surface, this study presents a theoretical solution for the anchoring force of three‐dimensional slopes and proposes a new optimization strategy for anchor force distribution. The method employed the Boussinesq solution from the field of elasticity. It led to the derivation of an equilibrium equation set, which incorporated the anchoring force increment. As a result, the approach yielded a more accurate theoretical value for a three‐dimensional anchoring force. In practical engineering applications, the prestress of anchor cables is often uniformly set, which may lead to discrepancies in the anchoring force requirements at different locations on the slope, potentially resulting in resource waste. The research introduces a linear programming approach to optimize resource allocation, aiming to minimize the total anchoring force under fixed anchor cable quantities, installation angles, and locations. Nevertheless, the results from the Simplex Method could lead to an overly concentrated distribution of anchoring force. Therefore, the study further employs the normal distribution theory to reallocate anchoring forces, thus achieving a more reasonable distribution. The proposed method has been validated through three example studies and a practical engineering case study, resulting in significant reductions in the total anchoring force following optimization. Moreover, such an approach allows for optimized handling of the anchoring force for each anchor cable. The work provides a new perspective and tool for practical engineering applications.

Longitudinal Seismic Response of Metro Tunnels Crossing a Fault with Multi-Slip Surfaces

There are multiple seismic fault zones near Xi’an in China, among which the Li Piedmont Fault has multiple slip surfaces. A 3D finite element dynamic Soil–Fault–Tunnel model was established based on the engineering background of the Xi’an Metro tunnel orthogonally crossing the Li Piedmont Fault. The input seismic loads used the Chi-Chi, El-Centro, and artificial seismic waves, and the latter was artificially synthesized based on seismic conditions and site conditions of actual engineering. The Chi-Chi seismic wave with larger PGV/PGA and wider acceleration-sensitive area is a near-field seismic wave, while the others are far-field seismic waves. The seismic loads were transformed into the equivalent nodal force on the boundary nodes of the model, and nonlinear dynamic calculation was carried out to obtain the longitudinal seismic response of the structure. The main results show that the fault amplifies the seismic response of the tunnel, and the tunnel at the position of the fault slip surfaces is more vulnerable to failure, especially near the slip surface between the hanging wall and the fault, where the maximum acceleration, soil pressure, and internal force of the tunnel structure occur. In addition, the seismic response of the tunnel and soil caused by near-field seismic motion is significantly stronger than that caused by far-field seismic motion.

Predicting Slip Surfaces for Slope Stability Assessment Along Highway 80 in Mosul, Northern Iraq

Predicting Slip Surfaces for Slope Stability Assessment Along Highway 80 in Mosul, Northern Iraq

Evaluating stability of rigid-column-supported and geosynthetic-reinforced embankments

Field observations and centrifuge tests indicate that progressive column bending failure accompanies most instabilities of rigid-column-supported and geosynthetic-reinforced (RCGR) embankments. However, recognized guidelines specifically for evaluating the overall stability of such systems featuring bending failure remain limited. A general methodology to calculate the factor of safety (FS) for RCGR embankments using the limit equilibrium method is presented in this article. The focus is on deep-seated slope failures, wherein rigid columns progressively fracture due to subsoil overstressing. The concentric arches model, along with tensioned geosynthetic analysis, informs the determination of vertical and horizontal loads on the column heads. The column's resisting moment stems from its flexural and compression resistance. A mobilization factor for the net thrust on each column is defined to capture the progressive failure. The methodology involves an iterative computational procedure to identify the critical slip surface and the FS using the Fellenius' method. The solution was validated using three case studies, including both centrifuge models and field tests, as well as finite-element analysis. The results indicate that the soil mass contributes the most to resisting sliding and overall stability, followed by columns and geosynthetics. In addition, axial force mainly provides the resisting moment of columns.

A new approach to determining the slip surface in tuff to determine the volume of landslide material: A case study on the West Sinjai road section, Sinjai Regency, South Sulawesi, Indonesia

Analysis of landslide slip surface based on the engineering properties of tuff rocks, including shear strength, water content, and infiltration rate on the West Sinjai road section, South Sulawesi, Indonesia. This study aimed to analyze the effect of shear strength, water content infiltration rate, and weathering grade of tufa rocks in the study area. The methods used in this study area included a study of weathered tuff profile characteristics, weathered tuff infiltration testing and residual soil (RS) determination of weathered tuff water content and residual soil, and testing of shear strength of weathered tuff and residual soil. This research used aspects of engineering geology, including shear strength, water content, and infiltration rate, as well as rock weathering grade to determine the slip surface in tuff to determine the volume of landslide material. The results showed that the tuff profile consisted of four grades, namely moderately weathered tuff (MW), highly weathered tuff (HW), completely weathered tuff (CW), and soil residual (RS). The rate of tuff infiltration increases with increasing weathering grade. The water content is more significant with the high degree of weathering of tuff. At the same time, the shear strength decreases with high weathering. Therefore, the research area is prone to landslide events. The slip surface is in a layer of moderately weathered tuff rock (MW), and those that experience landslides are highly weathered tuff rock (HW), completely weathered (CW), and residual soil (RS).

FORMATION OF THE NEAR-FAULT DAMAGE ZONE DURING DYNAMIC RUPTURE IN A CRYSTALLINE ROCK MASS

Many models for analyzing the dynamic propagation of seismogenic ruptures are based on solving classical problems of fracture mechanics. It is assumed that the fault is a shear fracture mode with uniformly distributed friction and stresses at the crack tip. Known fracture mechanics theories do not describe the formation of laterally oriented damage zones, i.e., in the direction perpendicular to the crack plane. Observational data indicate the presence of a fairly extensive zone of damaged material in the vicinity of the fault. This is the zone of dynamic influence where the material has an increased number of fractures, higher permeability and lower elastic wave velocities. A correct assessment of the properties and sizes of zones of dynamic influence is crucial for constructing adequate earthquake preparation models. This paper analyzes the development patterns and quantitative characteristics of the damage zone during dynamic earthquake rupture and quasi-static evolution of the fault. To estimate the size and mechanical characteristics of the near-fault damage zone caused by movement along the slip surface, it is convenient to use the value of the second invariant of the deviatoric stress tensor (shear intensity). Matching of the calculated value with one or another degree of rock mass damage can be done using measurement data from large-scale explosions, by comparing them with the calculation results. It is shown that coseismic movement along the fault leads to insignificant changes in the properties of the host rock mass. Although the longitudinal wave velocity near the fault decreases markedly by 30-35%, the permeability increases only by approximately a factor of three, and the increase in the degree of fracturing is almost unnoticeable. This means that the properties of the rock mass change due to the opening of preexisting cracks. Repeated movements do not radically change the characteristic dimensions and properties of the damage zone. It is concluded that the fault-affected zone is formed mainly at the quasi-static stage of the formation of a single main fault zone through the coalescence of individual macrofractures, and future seismogenic movements add to the already existing amount of fractures.

DIFFERENT-SCALE HETEROGENEITIES IN SEGMENTS OF SEISMOGENIC FAULTS AND THEIR INFLUENCE ON SLIP MODES

The paper presents some multidisciplinary research results on the structure of slip surfaces in segmented sections of tectonic faults in the Baikal region and Mongolia. The properties of subsurface (modern) and deep slip planes that came to the earth’s surface as a result of many-kilometer denudation in the upper part of the earth’s crust are studied at different levels-from macroscale to nanocrystals. Other types of heterogeneities characterizing the structure of fault slip zones are also considered. The presented data indicate a heterogeneous structure of tectonic faults. Their slip zones show both low friction in sections where strong mineral phases are replaced by weak minerals, and potentially unstable patches with high frictional resistance. The results obtained in a comprehensive study of geological conditions, under which different-scale heterogeneities emerge in exhumed fault segments, should be taken into account when developing rock mass models suitable for numerical simulation of earthquake preparation processes at the micro-, mesoand macroscales.

Analysis of a Nailed Soil Slope Using Limit Equilibrium and Finite Element Methods – A Review

Reviewing the two most used techniques for slope stability analysis is the goal of this research. The analysis derived from PLAXIS 2D (finite element based) and SLOPE/W (limit equilibrium based). Two 45degree and 60-degree slope angles that are strengthened with nails at three different inclinations—0, 15, and 30—are used for the analysis. All nail inclinations and slope angles are measured from the horizontal. A comparative analysis of stability metrics, including critical slip surfaces, nail forces, and factor of safety, has been conducted. It is discovered that the limit equilibrium approach produces greater values of the factor of safety when compared to the finite element method. There are notable differences between the failure surfaces obtained from the two methods.Large nail forces are seen using the LEM approach for 45 slopes with all nail inclinations, however the FEM method indicates an increase in the nail forces for 60 slope angles. In conclusions, both FEM and LEM methods have advantages and disadvantages. These two methods give the precise results if both methods are combined. The analysis using the LEM to compute the factor of safety are further enhanced with the Finite Element using PLAXIS 3D to compute the stress strain displacement of the soil with added soil nailing or structure member such as retaining wall.

Microstructural comparison in fault gouges and slip surfaces of active and inactive faults: A case study at Watarigawa area in northeastern Yamaguchi Prefecture, SW Japan

Microstructural comparison in fault gouges and slip surfaces of active and inactive faults: A case study at Watarigawa area in northeastern Yamaguchi Prefecture, SW Japan

Stress-strain response and deformation behavior of hydrate-bearing sands under different grain sizes: A particle-scale study using DEM

Natural gas hydrates are crystalline solids found in sediments beneath the seabed and permafrost, which significantly affect the mechanical behavior of sediments. The effect of hydrates often varies for different sediments, which has been captured in some laboratory studies. But the particle-scale information involved is obscure and the underlying mechanisms often rely on assumptions. In this study, discrete element method (DEM) was used to improve understanding of the hydrate effect on the mechanical behavior of different sands. Triaxial compression tests were carried out using DEM on the digital hydrate-bearing sands (HBS) with different grain sizes. Simulation results shows that the large-grain samples often yield earlier and tend to strain-hardening behavior, while hydrate occurrence induces strain-softening behavior. In terms of stress-strain response and porosity changes, the hydrate strengthening on the small-grain samples is much greater than the large-grain samples. Particle-scale observations indicate that particle rotation usually occurs in regions with small particle displacement and is more intense on shear slip surfaces. Hydrate bonds are mainly subjected to tensile failure, and large grain size may hinder bond shear failure. Hydrates restrict the development of radial fabrics and enhance the stress-induced anisotropy, rendering a more stable framework for sediments.

Dynamic analysis of MSE wall subjected to surface vibration loading

Abstract Extensively used Mechanically Stabilized Earth (MSE) walls in Rail Transportation System (RTS) are vulnerable to surface vibrations generated by moving vehicles. Hence, it is necessary to consider the effects of surface vibrations during the design of MSE walls for RTS. Steel-reinforced panel-type MSE walls are shown to perform well during vibration loading, but costly steel materials have led to greater reliance on affordable and readily available geosynthetics for reinforcement. Limited research exists on the behavior of panel-type MSE walls with geosynthetics considering RTS-induced vibrations frequencies. Thus, this study employs Finite Element software PLAXIS 3D to simulate the impact of surface vibration frequencies on panel-type MSE walls. The qualitative study encompasses two reinforcement cases (geogrids and steel strips) of 4 m MSE wall height and four harmonic loading frequencies representing RTS-induced surface vibrations for simulation. The dynamic responses of MSE wall are presented in terms of lateral wall displacements and lateral earth pressure distributions. Furthermore, the distributions of tensile strain and the identification of potential slip surface locations are presented. The findings indicated that MSE wall and reinforcement responses are governed by RTS-induced vibrations and fundamental frequency of backfill soil. This highlights the need for consideration of both the fundamental frequency of the backfill soil and RTS-induced vibrations in the design of MSE walls.

Meshless numerical manifold method with novel subspace tracking and CSS locating techniques for slope stability analysis

The meshless numerical manifold method (MNMM) inherits the advantages of handling continuous and discontinuous problems uniformly, improving interpolation precision, and avoiding linear dependence issues. This paper refines the MNMM method for slope stability analysis to overcome the dependence and sensitivity of the strength reduction method of the finite element method on the number of finite element meshes and the algorithm for solving the nonlinear equations when calculating slopes with soft and weak interlayers. First, the strength reduction method (SRM) was incorporated into MNMM to create the numerical model called MNMM-SRM. Based on the MNMM-SRM, a complementary Mohr-Coulomb (M−C) control equation compliant with Koiter's rule of multi-yielding surfaces was established. In the principal stress space, the subspace tracking method was used to track the eigenvalues and eigenvectors of the stress tensor, thereby addressing the corner problem of M−C multi-yield surfaces. Combining the k-means clustering algorithm with wavelet transformation and employing the slope's total nodal displacement field as an input variable, an intelligent and efficient critical slip surface (CSS) automatic extraction method was developed. Three typical cases were used to validate the accuracy of the numerical model. This numerical model has a wide range of potential applications in slope stability research.

Elastic–Plastic Analysis of Rigid Passive Piles in Two-Layered Soils

The paper analyses the behavior of a rigid passive pile embedded in a soil profile consisting of a stable layer underlying an unstable layer subjected to a uniform soil displacement. Pile-soil interaction is considered by modeling the soil by a series of elastic–plastic springs along the pile shaft. The modulus of horizontal subgrade reaction is assumed to linearly increase with depth in the unstable layer and constant in the stable one. The ultimate soil resistance is assumed increasing with depth in both layers. The results of analysis are presented in dimensionless form in terms of shear force developed at the slip surface as a function of the pile embedment into the stable layer and the distribution of soil characteristics over depth. The method allows capturing pile response not only at the soil ultimate state but also at the intermediate states. Specifically, the governing equations for the elastic, elastic–plastic and plastic cases are discussed and, whenever possible, a set of closed-form expressions is provided to estimate the maximum bending moment along the shaft and the pile head deflection, so that for an assigned value of the required stabilizing force both ultimate and serviceability limit state of the pile can be checked. A numerical example is given to illustrate the application of the proposed procedure.

Texture evolution and strengthening mechanism of CuCrZr alloys during cold rolling

The evolution of microstructure and crystallographic texture in Cu–1Cr-0.061Zr alloy strips during multi-pass cold rolling deformation was studied. The results showed that the tensile strength of Cu–1Cr-0.061Zr alloy increased from 507 MPa to 683 MPa with increasing rolling strain, while the conductivity decreased from 84.1 to 68.1 of the International Annealed Copper Standard. When the strain is 1.86–3.85, the elongation is effectively stable at 7.5%–8.5%. The local strain and grain dislocation angle inside the alloy gradually increase with the increase in strain, and the grain orientation distribution becomes more uniform and stronger. The dislocation slip generated during the rolling process leads to the concentration of grain orientation toward the <11−1> direction, causing the Goss texture ({110}<001>) to gradually transform into a Copper texture ({112}<11−1>) with relatively stable grain orientation, which significantly improves the mechanical properties at the macro level. In addition, the heat generated during the cold rolling process causes the cancellation of heterologous dislocations on a certain slip surface, resulting in a decreased dislocation density and a slight growth of nanoprecipitates. Nanoprecipitation strengthening and grain boundary strengthening are the main strengthening mechanisms in the Cu–1Cr-0.061Zr alloy, while the strength contribution of banded Cr phase dispersion is relatively small.

Injection-induced fault slip and associated seismicity in the lab: Insights from source mechanisms, local stress states and fault geometry

Probing source mechanisms of natural and induced earthquakes is a powerful tool to unveil associated rupture kinematics. The source processes of failure and slip instability driven by stress loading are affected by fault geometry, but the source ruptures of injection-induced seismicity in relation to fault structures and local stress states remain poorly understood. We have conducted a series of fault reactivation and slip experiments on sandstone samples containing faults with different surface roughness (smooth saw-cut fault and fractured rough fault). We impose progressive fluid injection to induce fault slip, and simultaneously monitor the associated acoustic emission (AE) activity. Using high-resolution AE recordings, we perform full moment tensor inversion of all located AE sources, and investigate the changes of AE source characteristics associated with induced fault slip and their relation to fault roughness. For the complex and rough fault, we observe significant non-double-couple components of AE sources and a high degree of focal mechanism heterogeneity. The temporal changes of AE mechanisms associated with injection-induced fault slip on the smooth fault reveal increasing proportions of double-couple components and decreasing variability of AE focal mechanisms when approaching the onset of slip events. The observed inconsistency between the nodal planes of AE sources and the macroscopic fault plane orientation is attributed to the development of secondary fracture networks surrounding the principal slip surface. We analyze changes in the magnitude-frequency characteristics and source mechanisms of AEs with fault-normal distance, showing that for the smooth (mature) fault, Gutenberg–Richter b-value of on-fault seismicity is lower and focal mechanisms are less heterogeneous, compared to off-fault seismicity. Our results emphasize the important role of roughness-related changes in local fault geometry and associated stress heterogeneity for source mechanisms and rupture kinematics of injection-induced seismicity.

Tuning the Through-Plane Lattice Thermal Conductivity in van der Waals Structures through Rotational (Dis)ordering.

It has recently been demonstrated that MoS2 with irregular interlayer rotations can achieve an extreme anisotropy in the lattice thermal conductivity (LTC), which is, for example, of interest for applications in waste heat management in integrated circuits. Here, we show by atomic-scale simulations based on machine-learned potentials that this principle extends to other two-dimensional materials, including C and BN. In all three materials, introducing rotational disorder drives the through-plane LTC to the glass limit, while the in-plane LTC remains almost unchanged compared to those of the ideal bulk materials. We demonstrate that the ultralow through-plane LTC is connected to the collapse of their transverse acoustic modes in the through-plane direction. Furthermore, we find that the twist angle in periodic moiré structures representing rotational order provides an efficient means for tuning the through-plane LTC that operates for all chemistries considered here. The minimal through-plane LTC is obtained for angles between 1 and 4° depending on the material, with the biggest effect in MoS2. The angular dependence is correlated with the degree of stacking disorder in the materials, which in turn is connected to the slip surface. This provides a simple descriptor for predicting the optimal conditions at which the LTC is expected to become minimal.

Axisymmetric stagnation-point flow of non-Newtonian nanomaterial and heat transport over a lubricated surface: Hybrid homotopy analysis method simulations

Abstract The heat transfer phenomenon associated with the lubricated surfaces offers applications in the manufacturing processes, thermal systems, industrial systems, and engineering phenomenon. It is a well-established fact that improvement in heat transfer is recently successfully claimed with the interaction of nanoparticles. Following such motivation in mind, the prime objective of current continuation is to perform the prediction of heat transfer in second-grade material subject to the lubricated surface. The lubricants are filled with non-Newtonian power law material. The varying thickness of the thin lubricating layer permits an imperfect slip surface. The second-grade fluid interfaces with the boundary condition. The modified semi-analytical tool termed as hybrid homotopy scheme is used to perform the simulations. Shooting and homotopy methods are combined in this new approach. Relevant effects of parameters on physical phenomenon are explained. The importance of influencing parameters in relation to the velocity field, temperature, and concentration profiles is investigated graphically. It is claimed that analytical computations existed for shear thinning case. It is observed that there is a noticeable drop in concentration and thermal profiles due to the variation of viscoelastic parameter. The control of free stream velocity is claimed due to the interaction of slip parameters.

Stability analysis of rainfall-induced landslides: A case study of a hilly area in Bangladesh

Rainfall-induced landslides stand as the prevailing geohazard in tropical and subtropical regions. The ongoing global climatic changes have introduced a wave of anomalous rainfall events across the world. These abnormal weather patterns have triggered numerous landslide incidents, resulting in significant loss of life and property. To develop early warning systems for such threats to people in mountainous areas of Chittagong, Bangladesh, it requires an in-depth understanding of the geo-environmental properties of soil slopes under heavy rainfall. Historical records reveal that rainfall in total exceeding 150–250 mm has resulted in both localized slope collapses and debris floods. When it rains heavily, rainwater infiltrates initially unsaturated slopes, elevating the degree of saturation while decreasing soil suction. Consequently, the reduced shear strength along the critical slip surface diminishes the factor of safety (FoS), and slope failure occurs. As a result, studies of soil-water characteristics have been conducted, followed by laboratory testing at the impacted sites, and the study found that rainfall and soil type (fine-grained silt) were the most critical factors behind landslides. The mechanism of slope failure is also demonstrated using a simple numerical infiltration model and a slope stability equation. The soil characteristics, the saturated volumetric water content (θs), closely match the field water holding capacity (θf), with a minor difference of 4-8%, and the drainage condition at the bottom of the slope appear to be important factors. Application of these test results to an early warning system for landslides and flash floods is finally demonstrated based on some simplifying assumptions.

Effect of copula dependence structure on the failure modes of slopes in spatially variable soils

The copula dependence structure underlying the correlated shear strength parameters of soils can significantly affect the results of slope reliability analysis and risk assessment of slope failure. Currently, how do copula dependence structures affect the failure modes of slopes in spatially variable soils still remains an open question. This study systematically investigates the effect of copula dependence structures on the failure modes of a cohesive-frictional slope in spatially variable soils via an adapted random finite difference method (RFDM) that incorporates the copula-based random fields. The proposed RFDM proceeds with the simulation of cross-correlated random fields considering the copula dependence between the shear strength parameters of the slope. The strength reduction analyses are then performed within the framework of Monte Carlo simulation to obtain the stability analysis results, including the critical slip surface (CSS) and associated factor of safety (FS) and sliding volume. Finally, various statistical analyses on the number and distribution of CSS, FS and sliding volume as well as the failure modes versus different statistics of soil properties are analyzed considering different dependence structures. The results show that the overall distribution range of CSS obtained by the commonly used Gaussian copula is more concentrated, whereas the result by the No. 16 copula is the widest. The differences in the overall distribution range of CSS among different copulas decrease with the increase of the scale of fluctuation, coefficient of variation, and cross-correlation coefficient of the strength parameters. The proportions of different failure modes are comparable for the Gaussian, Plackett and Fran copulas, whereas the No.16 copula has the smallest proportion for the shallow failure and largest proportions for the deep and multi-slip failures. The influence of copula dependence structure on the slope failure mode is more significant than the statistical parameters of soil properties. The results provide useful references for copula selection when the underlying dependence structure is difficult to be determined.