非线性Mohr-Coulomb准则适用范围及其改进研究

Application scope of nonlinear Mohr-Coulomb criterion and its modification

SINGH M为克服(Mohr-Coulomb M-C)准则只能线性表征岩石强度随围压变化这一局限性,在M-C准则的基础上添加一个修正项对其进行改进,提出非线性M-C准则。该准则认为,岩石在围压达到其单轴抗压强度时岩石就进入临界状态,此观点与部分岩石的试验结果有较大的出入,使得该准则的适用范围受到影响。为拓宽非线性M-C准则的适用范围,通过对其修正项的进一步改进,提出M-C准则修正一般表达式。应用11种岩石三轴试验数据对M-C准则修正一般表达式、非线性M-C准则和目前岩石力学界认为较好的双曲线型准则的精度进行比较,结果显示,M-C准则修正一般表达式对岩石三轴强度的拟合精度高于其他两种准则,且由岩石三轴试验强度的一致性更好。证明M-C准则修正一般表达式优于非线性M-C准则,且适用范围更广。

SINGH M proposed a nonlinear Mohr-Coulomb（M-C） criterion by adding a correction term to the original M-C criterion which could only linearly express rock strength variation with confining pressure. The nonlinear M-C criterion assumes that there is a critical state when the confining pressure reaches the uniaxial compressive strength of rock material, however it has a large discrepancy with some triaxial experimental results. In order to expand the application of the nonlinear M-C criterion, a general expression of M-C criterion is developed by further improving the correction term. A comparison among the general expression of M-C criterion, the nonlinear M-C criterion and the hyperbolic model is made by using triaxial data of 11 different kinds of rock. Analytical results show that the M-C criterion with the modified expression has a higher accuracy than the other two criteria. The strength values predicted by the generalized M-C criterion is consistent well with experimental values. Thus, the generalized M-C criterion has wider application than the nonlinear M-C criterion.