To address the engineering problems of road subsidence and subgrade instability in aeolian soil under traffic loads, the aeolian soil was improved with rubber particles and cement. Uniaxial compression tests and Digital speckle correlation method (DSCM) were conducted on rubber particles-cement improved soil (RP-CIS) with different mixing ratios using the WDW-100 universal testing machine. The microcrack and force chain evolution in samples were analysed using PFC2D. The results showed that: (1) The incorporation of rubber particles and cement enhanced the strength of the samples. When the rubber particles content was 1% and the cement content was 5%, the uniaxial compressive strength of the RP-CIS reached its maximum. Based on the experimental results, a power function model was established to predict the uniaxial compressive strength of RP-CIS; (2) The deformation of the samples remains stable during the compaction stage, with cracks gradually developing and penetrating, eventually entering the shear failure stage; (3) The crack and failure modes simulated by PFC2D are consistent with the DSCM test. The development of microcracks and the contact force between particles during the loading are described from a microscopic perspective. The research findings provide scientific support for subgrade soil improvement and disaster prevention in subgrade engineering.

The delayed breakage of particles significantly affects the long-term mechanical properties of rockfill materials. This study examines the effects of particle strength dispersion on the distribution of time-dependent strength using fracture mechanics and probabilistic methods. Subsequently, the distribution of normalized maximum contact force (NMCF), defined as the ratio of the maximum contact force to instantaneous strength, for specimens with uniform particle size is derived using extreme value theory and Discrete Element Method (DEM). Based on this analysis, the probabilities of delayed breakage in rockfill specimens over various time intervals are calculated using a joint probability delayed breakage criterion. The feasibility of the proposed method is validated by comparing theoretical calculation with DEM triaxial creep simulation results that accounted for particle breakage. The findings offer innovative tools and theoretical insights for understanding and predicting the particle delayed breakage behavior of rockfill materials and for developing macro-micro creep crushing constitutive models.

This paper addresses the issue of crack expansion in adjacent buildings caused by foundation pit construction and develops a predictive model using the response surface method. Nine factors, including the distance between the foundation pit and the building, soil elastic modulus, and density, were selected as independent variables, with the crack propagation area as the dependent variable. An orthogonal test of 32 conditions was conducted, and crack propagation was analyzed using the FEM-XFEM model. Results indicate that soil elastic modulus, Poisson's ratio, and distance between the pit and building significantly impact crack propagation. A predictive model was developed through ridge regression and validated with additional test conditions. Single-factor analysis showed that elastic modulus and Poisson's ratio of the silty clay layer, elastic modulus of sandy soil, and pit distance have near-linear effects on crack propagation. In contrast, cohesion, density, and Poisson's ratio of sandy soil exhibited extremum points, with certain factors showing high sensitivity in specific ranges. This study provides theoretical guidance for mitigating crack propagation in adjacent buildings during excavation.

The fracture network of hydraulic crack is significantly influenced by the bedding plane in coalbed methane extraction. Under mode II loading, crack deflection holds a key position in hydraulic cracking, especially in hydraulic shearing. This study first analyzed the crack deflection theory of layered rock. The semi-circle bending test under asymmetric loading is performed, and the four-dimensional Lattice Spring Model (4D-LSM) is established to examine how the bedding parameters affect coal crack propagation under mode II dominant loads. The 4D-LSM results are comparable to the coal loading test results under quasi-mode II and the analytical prediction of crack deflection theory. During mode II loading, the coal crack propagation is greatly influenced by the angle, strength, and elastic modulus of the bedding plane, while the effects of thickness and spacing of bedding are insignificant. The crack of coal tends to propagate towards the bedding, following a decrease in bedding angle, a decrease in bedding strength, and an increase in elastic modulus. With higher bedding strength, spacing, and thickness, the peak load on the coal sample is higher. The influences of bedding strength, elastic modulus, spacing, and thickness on the peak load of coal samples and its anisotropy gradually decrease. It is proved that compared with the tangential stress ratio and traditional energy release ratio theories, the corrected energy release ratio criterion can more accurately predict the direction of crack deflection of coal, especially under mode II loading. The results can provide assistance in the design of initiation pressure and fracturing direction in coal seam hydraulic fracturing. (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/).

Particle breakage and its effect on granular materials have a significant influence on the shear strength and compressibility of soil specimens. While the majority of studies have focused on the drained condition, the current research explores the particle breakage under undrained conditions. A combined discrete element method (DEM) and extended finite element approach has been used to simulate the biaxial loading. The model enables simulation of the crack propagation path and progressive strength reduction of particles in a computationally efficient approach. Moreover, a novel scheme by using variable time-steps has been employed in the DEM simulations to reduce the computational cost. The results, in qualitative agreement with those from experimental studies, show that the particle breakage causes a decrease in shear strength and dilative behavior and an increase in the induced pore water pressure. The findings indicate that the particle breakage under drained conditions is significantly higher than under the undrained conditions. The results suggest that the pore water pressure creates a hydrostatic-cushioning effect between particles and reduces the magnitude of the contact forces. This ultimately increases the relative density of the assembly, which increases the rate of particle breakage.

Asa calculation method based on the Galerkin variation, the numerical manifold method (NMM) adopts a double covering system, which can easily deal with discontinuous deformation problems and has a high calculation accuracy. Aiming at the thermo-mechanical (TM) coupling problem of fractured rock masses, this study uses the NMM to simulate the processes of crack initiation and propagation in a rock mass under the in fluence of temperature field, deduces related system equations, and proposes a penalty function method to deal with boundary conditions. Numerical examples are employed to con firm the effectiveness and high accuracy of this method. By the thermal stress analysis of a thick-walled cylinder (TWC), the simulation of cracking in the TWC under heating and cooling conditions, and the simulation of thermal cracking of the Swedish & Auml;sp & ouml; Pillar Stability Experiment (APSE) rock column, the thermal stress, and TM coupling are obtained. The numerical simulation results are in good agreement with the test data and other numerical results, thus verifying the effectiveness of the NMM in dealing with thermal stress and crack propagation problems of fractured rock masses. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting 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/).

Strengthening interconnection and interoperability between water supply groups and reservoirs in super mountainous cities, a large number of water conveyance tunnels need to be built. Jacking prestressed concrete cylinder pipe (JPCCP) has been applied to pipe jacking construction in soil stratum. A new type of JPCCP was proposed to meet the needs of long-distance pipe jacking construction of water conveyance tunnels in rock stratum. However, the frictional resistance of the rock mass-pipe interface is very complicated in engineering practice. It is common for pipe sections to become stuck due to the excessive friction. The mechanical response and deformation characteristics of the new JPCCP when pipe sticking problem occurred have attracted more and more attention. In this paper, the characteristics of concrete strain, steel stress, crack propagation and axial stress transfer under axial jacking force were studied by the combined method of fullscale test and numerical simulation. The full-scale tests results showed that the concrete internal strain and surface strain of the pipe increased with the increase of the axial jacking force. The spigot end was the weakest area, where cracks appeared first and then developed along the circumferential direction in the full-scale tests. The potential causes of pipe cracking in full-scale tests were carefully discussed. It is suggested to improve the mechanical performance of the spigot end. Finally, the numerical simulations further revealed the axial stress transfer characteristics of the new JPCCP.

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.

Due to the presence of ice and unfrozen water in pores of frozen rock, the rock fracture behaviors are susceptible to temperature. In this study, the potential thawing-induced softening effects on the fracture behaviors of frozen rock is evaluated by testing the tension fracture toughness ( K IC ) of frozen rock at different temperatures (i.e. - 20 degrees C, - 15 degrees C, - 12 degrees C, - 10 degrees C, - 8 degrees C, - 6 degrees C, - 4 degrees C, - 2 degrees C, and 0 degrees C). Acoustic emission (AE) and digital image correlation (DIC) methods are utilized to analyze the microcrack propagation during fracturing. The melting of pore ice is measured using nuclear magnetic resonance (NMR) method. The results indicate that: (1) The K IC of frozen rock decreases moderately between - 20 degrees C and - 4 degrees C, and rapidly between - 4 degrees C and 0 degrees C. (2) At - 20 degrees C to - 4 degrees C, the fracturing process, deduced from the DIC results at the notch tip, exhibits three stages: elastic deformation, microcrack propagation and microcrack coalescence. However, at - 4 degrees C-0 degrees C, only the latter two stages are observed. (3) At - 4 degrees C-0 degrees C, the AE activities during fracturing are less than that at - 20 degrees C to - 4 degrees C, while more small events are reported. (4) The NMR results demonstrate a reverse variation trend in pore ice content with increasing temperature, that is, a moderate decrease is followed by a sharp decrease and - 4 degrees C is exactly the critical temperature. Next, we interpret the thawing-induced softening effect by linking the evolution in microscopic structure of frozen rock with its macroscopic fracture behaviors as follow: from - 20 degrees C to - 4 degrees C, the thickening of the unfrozen water film diminishes the cementation strength between ice and rock skeleton, leading to the decrease in fracture parameters. From - 4 degrees C to 0 degrees C, the cementation effect of ice almost vanishes, and the filling effect of pore ice is reduced signi ficantly, which facilitates microcrack propagation and thus the easier fracture of frozen rocks. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting 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/).