砂岩力学特性对干湿循环效应响应规律的试验研究

为研究砂岩力学特性对干湿循环效应的响应规律,基于不同干湿循环作用下砂岩吸水性、单轴压缩与直剪试验结果,系统分析了砂岩吸水率、抗压强度、变形参数、抗剪参数以及破坏特征等物理力学特性对干湿循环效应的响应规律. 研究结果表明,随着干湿循环次数的增加,砂岩吸水率与质量损失率呈正相关变化,而抗压强度、弹性模量、黏聚力和内摩擦角则呈负相关关系,当循环15次时,与天然状态相比,砂岩抗压强度下降幅度高达78.96%,而黏聚力和内摩擦角则分别减小了78.40%和31.33%. 但不论曲线变化趋势是增大还是减小,其变化幅度均是先大后小,并最终会以某一循环次数为临界值发展变化. 砂岩的破坏特征亦会受到干湿循环试验次数的影响,干湿次数越少,脆性破坏越明显,反之则延性特征增强,即砂岩会呈现一种从脆性到延性转化的破坏规律. 

Mechanical Properties Response of Sandstone to Cyclic Drying-Wetting Effect

Based on water absorptivity tests, single compression tests and shear tests of sandstone under the different times of drying-wetting cycle, the response rules of physical mechanical behaviors of sandstone to cyclic drying-wetting effect such as deformation behavior, intensity behavior and failure characteristic are analyzed systematically in this paper. The tests results show that the relation between water absorption, quality loss rate and drying-wetting cycle effect is positive related, while the relations between compression strength, elastic modulus, cohesive force, inter friction angle and drying-wetting cycle effect is negative correlated. Comparing with native state, when the times of drying-wetting cycle is 15, the decrease range of compression strength is up to 78.96%, and cohesive force and inter friction angle are also down 78.4% and 31.33% respectively. In addition, the need to point out that no matter the change trends of curves are increase or decrease, its rangeability is all "big then small", and finally tends to a constant. The failure characteristics of sandstone are also influenced by drying-wetting cycle effect: the less the test times are done, the more obvious the brittle damage characters is, conversely the stronger the ductility characters is, that is, with the strengthen of drying-wetting effect, the sandstone damage present a transformation law from brittleness to ductility.