Internal state variable creep constitutive model for the rock creep behavior

摘要

The phenomenon that the rock deformation increases with time at a state of constant stress is termed as creep behavior ofrocks. The creep behavior and creep constitutive model of rock are important for understanding and analyzing the timedependentgeological movements and predicting the long-term stability of underground facilities in rock engineering. Twosets of triaxial creep tests were conducted on mudstone and diabase specimens, and one set of uniaxial creep test was conductedon sandstone specimens to investigate the creep behavior of rocks subject to different stress-strain loading histories.The creep behaviors of the three types of rocks were analyzed, and the creep strain versus time and creep strain rate versustime relations were obtained. The applicability of conventional time-dependent creep constitutive model in describing thecreep behavior under complex conditions was discussed. Based on the internal state variable theory, an internal state variablecreep constitutive model for the rock creep property was proposed, in which the irreversible axial strain was consideredas the internal state variable. The fitting of test data into the strain-dependent hardening law showed that it was capable ofdescribing the creep behavior of rocks experienced complex stress-strain loading histories.