Permeability evolution of low-permeability rocks in triaxial creep tests

In order to investigate the permeability properties of low-permeability rock during the whole process of creep, a series of triaxial creep tests for monzonitic granite with different confining pressures and seepage pressures are carried out using the multi-step loading procedure. Based on the experimental results, the permeability evolution law of the low-permeability rock during the creep period was analyzed, especially under the low stress level and failure stress level. The relation between permeability and volumetric strain was also discussed. The results show that the permeability keeps steady under low stress level, while increases significantly as the stress level reaches to the failure stress. Meanwhile, the rate of permeability change has a similar law with the creep strain rate. The permeability experiences with a trend of nonlinear decreasing rate in a primary creep stage, grows linearly in a secondary creep stage, and finally exhibits an accelerated increasing rate when tertiary creep occurs. ©, 2015, Academia Sinica. All right reserved.