Study of Triaxial Creep Properties of Purple Mudstone under Stepwise Loading
分级加载条件下紫色泥岩三轴蠕变特性研究

Rheological properties is an important mechanical properties of rock material. Triaxial creep properties of specimen made of purple mudstone were studied under stepwise loading. The experiment was carried out on a home-made gravitation lever style rock creep test machine and a triaxial pressure cell. Results show that under the same axial pressure,the greater the confining pressure is,the smaller the instantaneous elastic deformation and creep deformation of purple mudstone are;under the same confining pressure,the greater the axial pressure is,the larger both deformations are;the creep rate of purple mudstone has the same trend,and under the same axial pressure,the greater the confining pressure is,the fuzzier the creep rate at the stable creep stage is. In addition,results of the linear regression for stress and instantaneous strain show that the instantaneous axial strain and axial load approximated to grow proportionally. Through analyzing the purple mudstone creep curve trend,it is suggested that H/M model is reasonable to creep simulation. In order to implement the model parameters fitting,the nonlinear regression analysis of MATLAB software was adopted. Final results show that the maximum deviation between experimental curve and theoretical one is about 2e-5. This proves that H/M model can reasonably describe the creep properties of purple mudstone.