The sliding process of the landslide is gradual, and it is impossible for all points on the sliding surface to be in the state of peak shear stress. Therefore, it is reasonable and necessary to consider the stability calculation of the progressive failure process of landslide. In view of the existing stability analysis methods considering progressive failure of landslides, it is unreasonable to define key blocks incorrectly and adjust sliding surface parameters at different stages to consider the stress softening phenomenon of soil mass, which causes damage to the continuity of shear stress and strain curve of soil mass. To more closely consider the progressive process of landslide failure and more accurately describe the different stress states of each point on the sliding surface, the concept of landslide key block is proposed. The concept of the key block of landslide is put forward, and the displacement of landslide is introduced into the stability analysis of landslide by a new shear stress model. Based on the unbalanced thrust method, a new displacement-resistance method (NDR) is established, and the calculation formula of landslide stability is given.

Ensuring the stability of the surrounding rock mass is of great importance during the construction of a large underground powerhouse. The presence of unfavorable structural planes within the rock mass, such as faults, can lead to substantial deformation and subsequent collapse. A series of in situ experiments and discrete element numerical simulations have been conducted to gain insight into the progressive failure behavior and deformation response of rocks in relation to controlled collapse scenarios involving gently inclined faults. First, the unloading damage evolution process of the surrounding rock mass is characterized by microscopic analysis using microseismic (MS) data. Second, the moment tensor inversion method is used to elucidate the temporal distribution of MS event fracture types in the surrounding rock mass. During the development stage of the collapse, numerous tensile fracture events occur, while a few shear fractures corresponding to structural plane dislocation precede their occurrence. The use of the digital panoramic borehole camera, acoustic wave test, and numerical simulation revealed that gently inclined faults and deep cracks at a certain depth from the cavern periphery are the primary factors contributing to rock collapse. These results provide a valuable case study that can help anticipate and mitigate fault-slip collapse incidents while providing practical insights for underground cave excavation. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

In practical engineering, soil strength displays characteristics of spatial heterogeneity and anisotropy. Neglecting these characteristics complicates reliably evaluations of slope stability. Therefore, this study conducts an in-depth analysis of slope stability considering the spatial heterogeneity and anisotropy of soil strength. First, improvements were made to the existing spatial heterogeneity model and the original Casagrande anisotropy model to enhance their universality and practicality. Next, the spatial heterogeneity and anisotropy of soil strength were coupled and incorporated into the Mohr-Coulomb (M-C) strength criterion using an improved tensile-shear mode. Subsequently, within the framework of the limit equilibrium (LE) theory, a calculation mode of slip surface stress was employed to replace the conventional assumption mode of inter-slice force. This was achieved by constructing slip surface stress functions and introducing the concept of the local factor of safety for the slip surface, along with stress constraint conditions at the ends of the slip surface. This approach integrates the combined mechanisms of tension-shear and compression-shear, as well as the progressive failure modes of slopes. Finally, based on the overall mechanical equilibrium conditions satisfied by the sliding body, a rigorous LE solution for slope stability was established, accounting for the characteristics of the spatial heterogeneity and anisotropy in soil strength. Through comparative analysis of specific examples, the feasibility and effectiveness of the proposed method were validated. Additionally, this research can also be applied to thoroughly elucidate the slope failure mechanism influenced by the spatial heterogeneity and anisotropy of soil strength.

Surrounding rock deterioration and large deformation have always been a significant difficulty in designing and constructing tunnels in soft rock. The key lies in real-time perception and quantitative assessment of the damaged area around the tunnel. An in situ microseismic (MS) monitoring system is established in the plateau soft tock tunnel. This technique facilitates spatiotemporal monitoring of the rock mass's fracturing expansion and squeezing deformation, which agree well with field convergence deformation results. The formation mechanisms of progressive failure evolution of soft rock tunnels were discussed and analyzed with MS data and numerical results. The results demonstrate that: (1) Localized stress concentration and layered rock result in significant asymmetry in micro-fractures propagation in the tunnel radial section. As excavation continues, the fracture extension area extends into the deep surrounding rockmass on the east side affected by the weak bedding; (2) Tunnel excavation and longterm deformation can induce tensile shear action on the rock mass, vertical tension fractures (account for 45%) exist in deep rockmass, which play a crucial role in controlling the macroscopic failure of surrounding rock; and (3) Based on the radiated MS energy, a three-dimensional model was created to visualize the damage zone of the tunnel surrounding rock. The model depicted varying degrees of damage, and three high damage zones were identified. Generally, the depth of high damage zone ranged from 4 m to 12 m. This study may be a valuable reference for the warning and controlling of large deformations in similar projects. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

This study presents the classification and prediction of severity for brittle rock failure, focusing on failure behaviors and excessive determination based on damage depth. The research utilizes extensive field survey data from the Shuangjiangkou Hydropower Station and previous research findings. Based on field surveys and previous studies, four types of brittle rock failure with different failure mechanisms are classified, and then a prediction method is proposed. This method incorporates two variables, i.e. Kv (modified rock mass integrity coefficient) and GSI (geological strength index). The prediction method is applied to the first layer excavation of the powerhouse cavern of Shuangjiangkou Hydropower Station. The results show that the predicted brittle rock failure area agrees with the actual failure area, demonstrating the method's applicability. Next, it extends to investigate brittle rock failure in two locations. The first is the k0+890 m of the traffic cavern, and the second one is at K0-64 m of the main powerhouse. The criterion-based prediction indicates a severity brittle rock failure in the K0+890 m section, and a moderate brittle rock failure in the K0-64 m section, which agrees with the actual occurrence of brittle rock failure in the field. The understanding and application of the prediction method using Kv and GSI are vital for implementing a comprehensive brittle rock failure prediction process in geological engineering. To validate the adaptability of this criterion across diverse tunnel projects, a rigorous verification process using statistical findings was conducted. The assessment outcomes demonstrate high accuracy for various tunnel projects, allowing establishment of the correlations that enable valuable conclusions regarding brittle rock failure occurrence. Further validation and refinement through field and laboratory testing, as well as simulations, can broaden the contribution of this method to safer and more resilient underground construction. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The micro- to macro-scale pipeline-soil interaction mechanism in unsaturated granular soil remains unclear. This study investigates the unsaturated suction effect on the pipeline-soil interaction undergoing lateral ground movement using coupled discrete element method and finite element method (DEM-FEM) simulations. The Johnson-Kendall-Roberts (JKR) adhesive model was used to simulate the interparticle suction while the pipe segment was simulated with finite element meshes. The findings reveal that discontinuity and large deformation occurrences in unsaturated sandy soil in model tests can be successfully modelled by the DEM-FEM method. Besides, the interparticle suction effects on contact forces, particle collision behaviours, and special soil pressure distributions near the pipeline-soil interfaces were discovered and successfully explained. Additionally, progressive soil deformation and failure behaviours in dry and unsaturated soils were compared while the partial similarity between the suction effect and buried depth effect on pipeline-soil interaction was discussed. Finally, several conclusive pipeline-soil interaction failure patterns in different interparticle-suction conditions were identified after analysing a series of particle-scale behaviours including particle trajectories, particle contacts, and particle rotation distributions. The study indicated that neglecting the unsaturated effect can result in severely underestimating the intensity of pipeline-soil interaction and misjudging the soil failure patterns.

Marine-sensitive soils exhibit significant strength heterogeneity and nonlinear strain softening, which are vital characteristics in geotechnical engineering. This study introduces a novel soil strength formulation that effectively captures both of these key characteristics. This formulation is incorporated into the Mohr-Coulomb matched Drucker-Prager yield criterion. To address the mesh-dependence challenges typically encountered in classical finite element (FE) analysis for strain localization, this paper establishes a robust constitutive integration algorithm within the framework of Cosserat continuum theory. The numerical implementation is accomplished through the UEL function in the ABAQUS FE software. Following validation, the methodology is applied to conduct thorough FE analyses on the bearing capacity and progressive failure process of strip footings. Additionally, through parametric investigations, we explore the influence of nonlinear strain softening parameters and the heterogeneity parameter on the bearing capacity coefficient (Nc) and the underlying foundation failure mechanisms. By simulating the complete progressive failure process of the foundation, this numerical method exhibits its remarkable capability to accurately replicate the entire progressive instability process. Derived from parametric analyses, a remarkably accurate formula (Nc(lambda = 0)) is obtained, accounting solely for nonlinear strain softening. Furthermore, a comprehensive formula (Nc) is introduced, capturing both strength heterogeneity and nonlinear strain softening.

The failure of piles often starts from localized damage caused by stress concentration. However, little is known about such progressive process of pile failure involving crack initiation and propagation. Here, we propose a finite difference method (FDM)-discrete element method (DEM) coupling method to simulate the mechanical behavior of a slope reinforced by piles. The FDM is employed to model the macroscale behavior of the slope, while the DEM is employed to reveal the micro-mechanism of the progressive failure of anti-slide pile. The method is validated and then is used for mechanical analysis of a pile-slope system. The response of displacement, strain, and soil pressure is analyzed to investigate the failure mechanism of a slope reinforced with piles. The results show that slope deformation causes the initiation of cracks in the pile located proximal to the sliding surface, and the crack tip gradually expands as the breakage of the contact force chain in the pile until the pile completely fails. The progressive failure process of the pile is reproduced through monitoring the evolution of contact forces and the breakage of the contact force chains. The simulation of the interaction between soil and piles can be realized using the large-strain mode. Compared with conventional methods, the FDM-DEM coupling method considers detailed microscopic information with a lower computational cost, and provide a powerful tool for revealing the mechanical behavior of pile-reinforced slopes.

Cement-based columns in combination with geosynthetic reinforcement is a well-established soft ground improvement technique to enhance embankment stability. This paper aims to present a finite-element (FE) study based on a case history of a geosynthetic-reinforced column-supported (GRCS) embankment over soft soil. In this study, the columns are simulated with an advanced Concrete model to simulate the development of possible cracking and induced strain-softening. Numerical results are compared against published centrifuge tests, giving confidence to the established FE model with the Concrete model. New insights into the progressive failure mechanisms of GRCS embankments over soft soil are then discussed by examining the stress paths, internal forces, and cracks, as well as the plastic failure zones of columns. In addition, the role of columns and geosynthetics on the progressive failure mechanisms (failure loads and sequences) is also examined by an extensive parametric study. The results suggest that provided the optimization of compressive and tensile forces in the columns combined with the tensile stiffness of the geosynthetics is put in place, more columns can be mobilized to resist global sliding failure and to improve the bearing capacity of GRCS embankments.

The deformation of foundation soil caused by freeze-thaw cycles is a typical geological disaster in engineering construction in permafrost areas. Fiber optic sensing technology provides an important technical means for accurate and distributed real-time monitoring of frozen soil deformation. To explore the feasibility of distributed fiber optic strain sensing in monitoring frozen soil deformation, this study utilized a self-developed optical cable-frozen soil interface mechanical characteristics tester to investigate the failure mechanism of the cable-soil interface in frozen soil samples with different dry densities and initial water contents. The experimental results indicate that the fiber optic strain monitoring results accurately reflect the progressive failure characteristics of the cable-soil interface, and the strain softening model can better describe the mechanical properties of the interface. During the freezing process, the liquid water in the soil becomes ice, causing the movement of the freezing front and water migration, and resulting in significant differences in the mechanical properties of the interface. The evolution process of the shear stress at the cable-soil interface at different depths reflects the deformation coordination state with the frozen soil during the cable pullout process, indicating that the measurement range of the cable and the coupling of the interface are closely related to the dry density and initial water content of the soil. This study provides a reference for the application of optical fiber sensing technology in deformation monitoring of frozen soil foundation in cold regions.