考虑岩体本构及结构尺度效应的地下洞室模型有限元分析

Finite element analysis of underground opening model considering constitutive and structural size effects

对于地下洞室围岩稳定而言,存在两种尺度效应:一是本构尺度效应,二是结构尺度效应。在地下洞室模型的有限元分析中考察了两种尺度效应的作用。拟定了两种工况:①围岩中任一点的力学性质是该点到洞室中心距离的负幂函数,洞室由小到大,即同时考虑本构尺度效应和结构尺度效应;②围岩的力学性质一定,洞室由小到大,即只考虑结构尺度效应。对两种工况进行了平面应变弹塑性计算,分析了围岩中的应力、位移、及塑性区。从研究结果可知:当考虑岩体力学性质的尺度效应时,洞室围岩中的位移及塑性区均较小;而应力值较高,而不考虑岩体力学性质的尺度效应时的情况与之相反。

The authors think that there exist two kinds of size effects for the stability of surrounding rock mass of an underground opening; namely they are the constitutive size effect and the structural size effect. As a tentative inquiry, the authors try to investigate the actions of the two kinds of size effects in the finite element analysis （FEA） for an underground opening model. So two cases are assumed： the first one, the mechanical properties at any point in surrounding rock mass are the negative power functions of distance between the point and the opening center; and the opening span changes from small to large, that is, the constitutive size effect and the structural size effects are considered simultaneously; the second one, the mechanical properties of surrounding rock mass are constants, but the opening span changes from small to large; that is, only the structural size effect is considered. The elastoplastic calculations under a plane-strain condition are carried out for the two cases; and the stresses, displacements and plastic zones in the surrounding rock mass are analyzed. The results show that： the displacements and plastic zones in the the surrounding rock mass are smaller; and the stresses are comparatively large, considering the constitutive size effect of the mechanical properties; but the situation of without considering the constitutive size effect is the other way round.