不同应力路径下岩石三轴卸荷力学特性与强度准则研究

Experimental research on mechanical characteristics and strength criterion of rock of triaxial unloading tests under different stress paths

基于3种不同应力路径下花岗岩三轴卸荷试验，研究了岩石的应力-应变全过程曲线和变形特征及其强度准则。试验结果表明，卸围压过程中，侧向应变与围压先呈线性后呈非线性关系，且其增长速率约为轴向应变增长速率的3-5倍，表现出明显的侧向扩容，其扩容程度与卸载路径有关；从不同围压与体积应变曲线所围面积可以看出，卸荷前围压越大，卸荷释放的能量越大；变形模量随围压卸载而逐渐减小，且随初始围压增大，总体上呈负指数分布趋势，且同一种卸荷应力路径时，变形模量的减小量随初始围压增大有所增大，泊松比随围压降低而不断增大，两者之间呈现明显的非线性关系；岩石破坏特征以剪切破坏为主；采用幂函数型摩尔强度准则很好反应了岩石的强度特征。研究结果对地下金属矿深部开采具有一定的指导意义和参考价值。

By carrying out triaxial unloading test under different stress paths on rock, the complete stress-strain curves, deformation characteristics and its strength criterion are studied. The test results show that the relation between lateral strain and confining pressure firstly is linear, and then is nonlinear in the total stage of unloading confining pressure. And its growth rate is about 3 to 5 times the growth rate of the axial strain. It shows obvious lateral dilatancy, and the degree of dilatancy is related to the unloading path. According to the area that is enclosed by confining pressure and volumetric strain curve, it can be seen that the greater the confining pressure is before unloading, the more the energy releases. Deformation modulus decreases gradually with the unloading confining pressure, and increases with the initial confining pressure; the relation between deformation modulus and confining pressure shows negative exponential distribution overall. At the same unloading paths, the reduction of the deformation modulus increases with the increase of initial confining pressure. The Poisson′s ratio rises up continually, and the variation law with the confining pressure can be well described by nonlinear. Failure characteristics of rock are mainly shear failure. The strength characteristics of rock can be well characterized by using the Mohr strength criterion of power function. These conclusions provide reliable theoretical reference and guiding significance for the deep mining of the underground metal mine.