Sandstone widely occurs within the hydro-fluctuation belts of reservoir banks and is susceptible to progressive deterioration under repeated wetting-drying cycles, posing potential risks to long-term slope stability. To investigate this process, moderately weathered sandstone collected from a landslide hydro-fluctuation belt in the Three Gorges Reservoir area was subjected to 0-20 wetting-drying cycles. Uniaxial and conventional triaxial compression tests were conducted in combination with nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) to characterize the mechanical degradation and mesoscopic structural evolution of the rock. In addition, a two-dimensional numerical damage model incorporating mesoscopic heterogeneity was established based on continuum damage mechanics and the Weibull statistical distribution. The results show that wetting-drying cycles significantly reduce the peak strength, elastic modulus, cohesion, and internal friction angle of sandstone, exhibiting a clear nonlinear degradation trend. Meanwhile, the failure mode gradually evolves from shear-dominated brittle failure to a more ductile pattern characterized by multi-crack interaction. At the microscale, water-rock interaction and cement dissolution promote micropore development and connectivity, increasing intermediate pore volume and weakening the load-bearing skeleton of the rock. Numerical simulations reproduce the progressive evolution of microcracks into macroscopic conjugate fracture networks, providing a reliable basis for evaluating reservoir bank slope stability under cyclic wetting-drying conditions.
Heng Zhang, Shu Zhu, Liuming Chang, Zhicheng Wang, Jin Zhang, Xiangcheng Que — Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing 210098, China; School of Civil Engineering and Transportation, Hohai University, Nanjing 210098, China
Feiyang Wang — Department of Civil Engineering, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
Zhende Zhu — Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing 210098, China; School of Civil Engineering and Transportation, Hohai University, Nanjing 210098, China; College of Hydraulic and Civil Engineering, Xinjiang Agricultural University, Urumqi 830052, China
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