Empirical correlation for viscoelastic and viscoplastic deformation of structural planes under different normal stress conditions

Abstract

The creep behavior of rock mass, including structural plane creep and rock creep, is different from that of intact rock. It is generally recognized that the characteristics of structural planes play a crucial role in such creep behavior. However, currently there are few comprehensive systematic studies on the rheological properties of structural planes, including experimental and theoretical aspects. In this paper, marble with green schist’s weak structural planes from the Jinping secondary hydropower station were selected as samples, and multi-stage loading shear creep tests were carried out in order to analyze the shear creep characteristics of such structural planes under different normal stress conditions. The test results showed that the shear creep process of structural planes can be divided into three stages, namely the attenuation stage, the constant stage, and the accelerated creep stage. Furthermore, the degree of structural plane development and normal stress level have a great influence on the creep behavior of rock mass. Moreover, based on the testing results, we established a nonlinear viscoelastic-plastic shear creep model by adding a new rheological element to the classic Nishihara model. In addition, the comparison between the test data and the fitting curve showed that this new model could describe the viscoelastic and viscoplastic deformation of weak structural planes more accurately.