考虑蠕变效应的岩石损伤起始准则

现有的损伤起始准则多为应力的函数，即在应力空间中某一固定的曲面，得到的损伤起始面为介于初始屈服面与最终破坏面之间的固定曲面。基于现有损伤起始准则假定，考虑了蠕变变形的影响，提出了一种岩石损伤起始准则。该准则在应力空间中所形成的损伤起始面随着蠕变变形的增加而收缩。故此，根据该准则，岩石即使在应力水平低于瞬态损伤起始应力的情况下，也会随着时间的增加而达到损伤起始点，从而激活损伤过程直至达到最终的破坏状态。考虑蠕变效应的损伤准则可以很好地解释一些蠕变试验（包括常应变率试验、常加载速率试验和常应力蠕变试验等）结果。损伤起始准则中所包含的材料参数可以通过常规三轴试验和单轴蠕变试验很方便地确定。

Damage Initiation Criterion Considering the Creep Behavior of Rock

Most of the existing damage initiation criteria of rocks are functions of stress tensors,i.e.they are fixed surfaces in stress spaces.Hence the obtained damage initiation surface is a fixed surface between the initial yielding surface and failure surface.Based on assumptions in the existing damage initiation criterion,a damage initiation criterion for rocks taking creep deformation into account is proposed.According to this damage initiation criterion,the damage initiation surface in stress space will shrink with the increase of creep deformation.As a result,even when the stress levels are below the transient damage initiation values,damage will be activated due to the accumulation of creep deformation and will finally lead to rock failure.The damage initiation criterion could well explain the creep test results(such as results from constant strain rate tests,constant loading rate tests and constant loading creep tests).Parameters contained in the criterion can be identified by triaxial compressive tests and uniaxial creep tests.