Mesoscopic Damage Evolution of Water-Bearing Mudstone Under Low-Strain-Rate Cyclic Dynamic Loading: A Particle-Flow Simulation Study

Study on the damage evolution of red-bed soft rock in foundation pits under the coupled influence of drying-wetting cycles and cyclic disturbance

Taking argillaceous sandstone collected from foundation pits as the research object, laboratory tests including drying-wetting cycles, uniaxial compression, cyclic disturbance, and acoustic emission (AE) monitoring were conducted to investigate the deterioration and fatigue damage evolution laws. The results show that, under the influence of drying–wetting cycles, the compressive strength and elastic modulus of argillaceous sandstone both decline following a power-function attenuation trend, while the ultimate fatigue strain under cyclic disturbance rises, and the spatial distribution of AE events grows more scattered. In contrast, a higher upper-limit stress ratio yields a lower ultimate fatigue strain and induces more significant spatial clustering of AE events along the shear failure plane. After being subjected to drying-wetting cycles, the fatigue failure threshold of argillaceous sandstone remains stable within the range of 75%–80% σ . Fatigue life presents a log-linear correlation with the upper-limit stress ratio, and varies in accordance with a power function against the number of drying-wetting cycles. On this basis, a three-dimensional quantitative model was established to characterize the fatigue damage evolution of argillaceous sandstone. The research findings can provide a scientific basis for the design, construction, and stability control of foundation pits in red-bed soft rock.

Dynamic Progressive Failure and Energy-Driven Damage Evolution of Coal–Sandstone Composite Specimens Under Impact Loading: Coupling Effects of Component Ratio

Overburden rotation and mining disturbance promote deep coal fracture and spalling, potentially inducing dynamic hazards, while the coal–rock thickness ratio largely governs the composite’s dynamic response and failure severity. Based on the geological conditions of a typical deep coal mine, SHPB tests were performed on coal–sandstone composite specimens with four systematically varied coal-to-rock ratios (C:R = 1:0, 2:1, 1:1, and 1:2). High-speed photography and the digital speckle correlation method (DIC) were integrated to capture displacement, strain, energy, and fragmentation fields throughout progressive dynamic compression. Experimental data revealed four findings: (1) Crack development follows a sequential evolution process of initiation, propagation, and failure. Higher impact air pressure accelerates crack development and coalescence, resulting in a higher degree of specimen fragmentation and fewer large blocks. Within the tested range of coal–rock ratios, an increase in the rock proportion accelerates coal fracture, which is attributed to the significantly higher density and hardness of rock compared to coal. (2) Energy evolution consistently follows three stages: absorption, accumulation, and dissipation. Under identical impact pressure, a higher rock ratio elevates equivalent stiffness and wave impedance, leading to monotonic increases in peak stress, peak strain, absorbed energy, and dissipated energy. (3) The fragmentation degree exhibits a pronounced dependence on impact pressure. Specifically, for the pure coal specimen (C:R = 1:0), when the impact pressure increases from 0.3 MPa to 0.7 MPa, the mass percentage of coarse debris (>30 mm) drops from 73.37% to 18.57%, whereas that of fine particles (<4 mm) rises from 15.69% to 35.24%. (4) Under identical impact conditions, a higher rock proportion leads to increasing trends in all measured indicators, including peak stress, strain, and energy accumulation and dissipation, which are consistent with the superior mechanical properties of the rock. Based on these observations, it can be inferred that the wave impedance mismatch and stiffness ratio at the coal–rock interface play a key role in controlling stress wave transmission/reflection and strain incompatibility; however, the individual contribution of each factor warrants further dedicated investigation.

Influence of water saturation on sandstone strainburst failure under true-triaxial unloading with different intermediate principal stresses

Study on mechanical response and damage models of sandstone-shale interbedding under different cyclic loading modes

Mechanical response and failure mechanisms of sandstone under water–rock interaction: a multi-scale study and constitutive modeling

Research on the Macro‐Micro Energy Evolution Law and Segmented Damage Constitutive Model of Sandstone Under Dry‐Wet Cycles

The periodic fluctuation of reservoir water levels induces dry‐wet cycles, deteriorating sandy rock slope stability and potentially triggering collapses. This study investigates the degradation mechanism of Three Gorges Reservoir fine sandstone through uniaxial compression tests and PFC2D simulations under varying dry‐wet cycles. Key findings include: (1) Increasing cycles reduce uniaxial compressive strength and elastic modulus (showing “V‐shaped” and “N‐shaped” degradation trends), while permeability and porosity rise, and P‐wave velocity declines. (2) Crack growth is nonlinear, dominated by shear cracks and high‐angle microcracks, with force chains aligning with the loading direction. (3) Dissipation energy rate follows a “W‐shaped” trend, while elastic energy rate exhibits an “M‐shaped” pattern; both energies at crack initiation, damage, and peak stress correlate exponentially with cycle count ( K sd being more sensitive). (4) Dry‐wet cycles weaken intergranular bonds, reduce elastic energy storage ( U e ), increase dissipated energy ( U d ), lower M ‐value stability, and shift failure from brittle to ductile. (5) A Weibull‐based segmented damage model effectively simulates sandstone behavior under cyclic conditions. These insights enhance understanding of reservoir slope stability under hydrological fluctuations.