The shear behavior of rock is markedly affected by the presence of water. To study the influence of water on the shear behaviors of rock, a series of direct shear tests were conducted on intact sandstone specimens with different water soaking durations (from dried to saturated) under three levels of normal stresses. Before direct shear tests were performed, water absorption experiments were conducted to guide the different levels of water saturation required for the direct shear tests. The influences of water on shear stress-shear strain responses and peak and residual shear strength envelopes were investigated. The results show that soaking duration significantly impairs the peak and residual shear strengths and other shear properties (e.g., cohesion, friction angle and shear stiffness). The reductions in fracture energy and friction coefficient and the chemical and corrosive deterioration are the main mechanisms for the decrease of intact sandstone’s shear strength. A novel observation is that the failure patterns of specimens are sensitive to different water distributions. The results provided in this study reveal that the stability of rock engineering is affected by changes in water levels.

岩石的剪切行为受水的存在显着影响。为了研究水对岩石剪切行为的影响，在三个正应力水平下，对具有不同浸水时间（从干燥到饱和）的完整砂岩试样进行了一系列直剪试验。在进行直剪试验之前，进行了吸水试验，以指导直剪试验所需的不同水饱和度水平。研究了水对剪切应力-剪切应变响应以及峰值和残余剪切强度包络线的影响。结果表明浸泡持续时间显着损害峰值和残余剪切强度和其他剪切特性（例如，内聚力、摩擦角和剪切刚度）。断裂能和摩擦系数的降低以及化学和腐蚀劣化是完整砂岩抗剪强度降低的主要机制。一个新的观察结果是试样的破坏模式对不同的水分布很敏感。本研究提供的结果表明，岩石工程的稳定性受水位变化的影响。