水对软质砂岩加卸荷力学特性影响的试验研究

Research on the effect of water on mechanical properties of soft sandstone under loading and unloading conditions

文章进行了软质砂岩在饱水和干燥条件下的单轴、三轴加载以及卸围压试验。试验结果表明岩样加卸荷力学特性受水的影响显著。饱水状态下,砂岩的加载及卸荷强度均低于干燥状态岩石的强度;无论是干燥还是饱水状态,卸荷条件下砂岩的黏聚力相对于加载条件有所提高,而内摩擦角却降低。在围压大于5 MPa时,卸荷条件下的岩样峰值强度低于加载条件下的强度;卸荷试验与加载试验相比较,处于饱水状态的岩样,其黏聚力和内摩擦角的变化幅度远大于干燥状态的岩样。

The uniaxial loading, triaxial loading and confining pressure unloading tests were carried out on dry or water-saturated typical soft sandstone. The tests results show that water has great influence on the mechanical properties of soft sandstone under loading and unloading conditions. The strength of water-saturated sandstone is lower than that of the dry sandstone under either loading or unloading conditions. For both the dry and water-saturated sandstone samples, the cohesion under unloading condition is higher than that of loading condition, and on the contrary, the internal friction angle is lower. When the confining pressure is greater than 5 MPa, the strength of the sample under unloading condition is lower than that of loading condition; the results of unloading test and loading test show that the variations of cohesion and internal friction angle of water saturated sandstone samples are greater than those of dry samples.