干湿循环作用下砂岩的劣化及破坏特性研究

针对干湿循环作用下消落带砂岩岩体强度衰减易导致砂岩边坡失稳的问题,以三峡库区秭归县沙镇溪典型库岸边坡砂岩试样为研究对象,采用浸泡—烘干处理方式模拟岩石干湿循环过程,将试样分组进行单轴压缩试验和直接剪切试验研究,并通过数值模拟,从变形的角度分析破坏过程。结果表明:干湿循环对砂岩的劣化作用在初期表现强烈,随着循环次数增加,作用逐渐减弱;在相同循环条件下,砂岩的极限抗剪强度随法向应力的增大而增加,相同法向应力作用下砂岩极限抗剪强度随干湿循环次数的增加而减小;粘聚力和内摩擦角随着干湿循环次数的增加而逐渐减小,总劣化度逐渐增大。试验结果对水库砂岩边坡稳定性分析具有较强的参考价值。

Study on deterioration and failure characteristics of sandstone under effect of wet-dry cycle

Aiming at the problem from the strength reduction of sandstone mass at water-level-fluctuation zone that is prone to cause the instability of sandstone slope， the wet-dry cycle process of the rock is simulated with the treatment mode of soaking and drying by taking the sandstone samples taken from the typical reservoir bank slope at Shazhenxi Town of Zigui County within the area of the Three Gorges Reservoir as the study objective， for which the uniaxial compression test and the direct shear test are made on the samples in groups， and then the failure process is analyzed from the aspect of deformation through the relevant numerical simulation. The result shows that the effect from the wet-dry cycle on the deterioration of the sandstone appears strongly at the initial period of the cycle and then is gradually reduced along with the increase of the number of the cycle. Under the same cyclic conditions， the ultimate shear strength of the sandstone is increased along with the increase of the normal stress， while it is decreased along with the increase of the wet-dry cycles under the same effects of the normal stress. Moreover， the cohesion and internal friction angle are gradually decreased along with the increase of the number of wet-dry cycle. Meanwhile， the total degree of deterioration is increased gradually as well. The test result has a better reference value for the analysis made on the stability of reservoir sandstone slope.