不同加、卸载条件下片岩的变形特性试验研究

Experimental Research on Deformation Characteristics of Schist under Different Loading and Unloading Conditions

对丹巴电站调压井围岩的片岩试样进行了加载试验和卸荷试验研究,分别分析了常规三轴试验及加轴压卸围压、以相同速率同时卸轴压与围压的3种加、卸载方式下的应力-应变关系及整个加、卸载过程中变形参数的变化规律,分析表明:片岩在卸荷条件下表现出明显的脆性破坏特征,而且有强烈的扩容现象,卸荷条件下岩石的破坏也是由于扩容所引起的;卸荷会造成岩体变形模量迅速减小、泊松比迅速增大;试验采取的两种卸荷方式与常规三轴相比较,岩石试样从受力至破坏的整个过程中其变形模量和泊松比的变化趋势有明显的不同,尤其是在相同速率同时卸轴压与围压的卸荷方式对岩石的变形参数影响很大。

The loading and unloading test was carried out for schist specimen from the surrounding rock of surge shaft at Danba Power Station,and the stress-strain relationship under three different ways of loading and unloading condition is analyzed. This paper also analyzes the change of deformation parameters during the whole loading and unloading process. The results show that there are obvious brittle failure characteristics of the rock under the unloading condition,and the rock specimens show a strong volumetric dilatancy. And the rock failure is also due to volumetric dilatancy under the unloading condition. Unloading will cause that the rock mass deformation modulus decrease rapidly,and the Poisson’s ratio increases quickly. This paper compares two kinds of unloading triaxial test with ordinary triaxial test,and the research shows that the change trends of deformation modulus and Poisson’s ratio are obvious different during the whole loading and unloading process,especially for the unloading style when the confining and axial compression are unloaded at the same rate,it will have a great impact on the rock deformation parameters.