The deterioration of rock mass in the Three Gorges reservoir area results from the coupled damage effects of macro-micro cracks and dry-wet cycles, and the coupled damage progression can be characterized by energy release rate. In this study, a series of dry-wet cycle uniaxial compression tests was conducted on fractured sandstone, and a method was developed for calculating macro-micro damage (DR) and energy release rates (YR) of fractured sandstone subjected to dry-wet cycles by considering energy release rate, dry-wet damage and macro-micro damage. Therewith, the damage mechanisms and complex microcrack propagation patterns of rocks were investigated. Research indicates that sandstone degradation after a limited cycle count primarily exhibits exsolution of internal fillers, progressing to grain skeleton alteration and erosion with increased cycles. Compared with conventional methods, the DR and YR methodologies exhibit heightened sensitivity to microcrack closure during compaction and abrupt energy release at the point of failure. Based on DR and YR, the failure process of fractured sandstone can be classified into six stages: stress adjustment (I), microcracks equal closure (II), nonlinear slow closure (III), low-speed extension (IV), rapid extension (V), and macroscopic main fracture emergence (VI). The abrupt change in damage energy release rate during stage V may serve as a reliable precursor for inducing failure. The stage-based classification may enhance traditional methods by tracking damage progression and accurately identifying rock failure precursors. The findings are expected to provide a scientific basis for understanding damage mechanisms and enabling early warning of reservoir-bank slope failure. (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/).

Insight into the growth of internal microstructure and surface morphology is critical for understanding the robustness of red sandstone artifacts in frigid environments. Since freeze-thaw (F-T) cycles can exacerbate the surface deterioration of water-bearing sandstone, a series of investigation on fresh and weathered water-bearing sandstone samples with different F-T cycle numbers (i.e. 0-100) is performed in this study, including three-dimensional (3D) laser scanning, scanning electron microscope (SEM) and computed tomography (CT) scanning tests, thermal property tests, Brazilian tests, and multi-field numerical simulations. Our results demonstrate that with increasing F-T cycles, the surface fractal dimension and specific surface area of red sandstone samples increase, and the pore size distribution inside rocks shifts from ultrananopores (10-100 nm) to micro-pores (0.1-100 mm) and ultramicropores (100 mm & thorn;). Spatially, the pores generated by the F-T cycles are more prominent near the surfaces of rock samples. Numerical simulation indicates that the uneven pore distribution leads to surface degradation. After 100 F-T cycles, the intergranular (IG) cement of the samples cracks, and the IG fractures are widened; eventually, due to the structural integrity weakening, the tensile strength is drastically reduced by over half. The thermal properties of the water-saturated sandstone can be improved during the F-T cycles, and a strong coefficient of determination of 0.98 exists between the fractal dimensions of sandstone surface and the tensile strength. When assessing the mechanical properties of stone artifacts under F-T cycles, the morphological damage of red sandstone should first be investigated when in situ sampling is inappropriate. (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/).

The construction of fill slopes becomes a critical aspect when there is a need to change the terrain or create new terrain. However, due to the poor engineering properties of the fill material, especially when red sandstone with notable disintegration properties is used, the risk of slippage or collapse may occur. This material is prone to erosion and disintegration under the action of natural factors such as heavy rainfall, leading to severe soil erosion and slope instability. In addition, the construction of fill slopes inevitably causes the destruction of native vegetation, exacerbating environmental problems. To address these problems, an novel ecological approach for preventing water damage to red sandstone fill slopes was developed using the vegetation-high-performance turf reinforcement mat -anchor-drainage pipe-synergistic slope protection system. Three test red sandstone slopes with different protection methods (unprotected, three-dimensional (3D) protection mesh, and vegetation ecological protection system slopes) were constructed, and the feasibility and reliability of ecological protection against water damage to red sandstone fill slopes were analysed via the field test method. The results showed that the vegetation ecological protection system can effectively inhibit soil erosion and increase the survival rate of vegetation roots. Moreover, the the high-performance turf reinforcement mat provides a strong protective complex through interactions with vegetation roots, anchors, and drains, which significantly enhances slope stability. Under heavy rainfall conditions, the vegetation ecological protection system can effectively limit slope erosion due to water scour, thus maintaining the structural integrity of the slope.

In the engineering practices, it is increasingly common to encounter fractured rocks perturbed by temperatures and frequent dynamic loads. In this paper, the dynamic behaviors and fracture characteristics of red sandstone considering temperatures (25 degrees C, 200 degrees C, 400 degrees C, 600 degrees C, and 800 degrees C) and fissure angles (0 degrees, 30 degrees, 60 degrees, and 90 degrees) were evaluated under constant-amplitude and low-cycle (CALC) impacts actuated by a modified split Hopkinson pressure bar (SHPB) system. Subsequently, fracture morphology and second-order statistics within the grey-level co-occurrence matrix (GLCM) were examined using scanning electron microscopy (SEM). Meanwhile, the deep analysis and discussion of the mechanical response were conducted through the synchronous thermal analyzer (STA) test, numerical simulations, one-dimensional stress wave theory, and material structure. The multiple regression models between response variables and interactive effects of independent variables were established using the response surface method (RSM). The results demonstrate the fatigue strength and life diminish as temperatures rise and increase with increasing fissure angles, while the strain rate exhibits an inverse behavior. Furthermore, the peak stress intensification and strain rate softening observed during CALC impact exhibit greater prominence at increased fissure angles. The failure is dominated by tensile damage with concise evolution paths and intergranular cracks as well as the compressor-crushed zone which may affect the failure mode after 400 degrees C. The second-order statistics of GLCM in SEM images exhibit a considerable dependence on the temperatures. Also, thermal damage dominated by thermal properties controls the material structure and wave impedance and eventually affects the incident wave intensity. The tensile wave reflected from the fissure surface is the inherent mechanism responsible for the angle effect exhibited by the fatigue strength and life. Ultimately, the peak stress intensification and strain rate softening during impact are determined by both the material structure and compaction governed by thermal damage and tensile wave. (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/).