如美水电站花岗岩卸荷力学特性试验研究

Experiments on Granite Mechanical Properties under Unloading Condition of Rumei Hydro-power Station

在常规三轴试验和卸荷试验的基础上,对比了两种试验方案下岩石的变形特性、力学参数和破裂特征。研究结果表明:由于试验岩样固有脆性特性,峰前变形阶段为本实验主要阶段,因此将峰前变形阶段作为主要研究对象;卸荷试验中,泊松比总体呈增大趋势,相对于加载试验平均增大了52.5%~118.75%;卸荷试验中,岩石黏聚力相对加载实验降低了31%,内摩擦角相对加载试验增加了8%;卸荷试验中,岩石破坏张性破裂特征明显,各种级别张裂隙、剪裂隙以及张剪(压剪)裂隙发育,且沿各级张、剪裂隙发育的次级裂隙也较发育。

Based on the conventional tri-axial test and the unloading test of rock specimen,the deformation,related parameters and fracture characteristics of rocks under loading and unloading conditions are compared.The results are as follows.Due to the brittleness characteristic intrinsic of specimens,the prepeak deformation stage is the main stage of the experiment,so the pre-peak deformation stage is the main study object.Poisson ratio increases slowly in the process of unloading,and the amount is 112%～463%.Compared with loading test,the cohesion of unloading test reduces 31%,and the internal friction angle increases 8%.In unloading test,due to the influence of the axial force especially the unloading function,the rock fracture with a significant characteristic of tension,various levels tensile cracks,shear cracks and tensile-shear cracks（compression-shear cracks）grow,and the secondary cracks along the cracks at all levels develop.