Time effect of stress and deformation for surrounding rocks in deep-buried tunnels during unloading

摘要

The state of stress and deformation of surrounding rock in deep-buried tunnels provide important basis in the designing of underground engineering.The relationship of local additional stress and the size of defects as well as unloading time is established.Pointing at the stress concentration and relaxation induced by the internal defects of rocks.Then the integral expression parsing of surrounding rock was derived.The time effect of stress and deformation of surrounding rock was divided into unloading and stress relaxation stage, the approximate analytic expression of stress and deformation of surrounding rock was found out by successive approximation method.The approximate analytic formula considering of the influence of stress concentration in the internal of rock as well as the time effect of unloading, can be used to investigating the influence of stress and deformation form which caused by defects of different radius of stress concentration.Analytical results show that the local excess tensile stress concentrations in surrounding rocks appear during and after the process of unloading, and the deformation have an additional increase after unloading.