基于Hoek-Brown准则的隧洞围岩变形研究

Study of deformations of surrounding rock of tunnel based on Hoek-Brown criterion

由于在许多实际条件下,比如节理岩体中,线性的M-C准则不太适用,非线性的Hoek-Brown比较适用,因此,可以尝试使用这一非线性屈服准则对洞室变形进行研究。研究隧洞变形时,将围岩分为弹性区、应变软化区、塑性流动区。采用Hoek-Brown准则和非关联流动法则对洞室变形进行了理论推导;软化区域围岩参数随着塑性变形增加而变化,解析法难以求得应力,采用龙格-库塔方法进行数值计算,求解得到塑性软化区和流动区半径,并最终求得洞室变形。通过算例计算表明,在不考虑软化区和流动区时,方法和Carranza-Torres计算结果相差甚小;随着原岩应力的增加,膨胀角对洞室变形的影响增大。

In many practical situations, for instance, in jointed rock mass, linear M-C yield criterion may not be justified and a nonlinear Hock-Brown yield criterion would be more appropriate, so it is necessary to attempt to calculate deformation of tunnel by the criterion. The surrounding rock is divided into three zones： elastic zone, strain softening zone and plastic flow zone. Theoretical derivation on deformation is carried out by Hock-Brown criterion and non-associated flow rule. Parameters of surrounding rock in strain softening zone are variable and they depend on the plastic deformation of this zone, so it＇s difficult to derive the analytical solution for stress in this zone. Runge-Kutta method is used to carry out numerical calculation and the radiuses of strain softening zone and plastic flow zone are calculated. Finally, the deformations of tunnel are calculated. It is demonstrated by an example that the results calculated by the method in this paper and Carranza-Torres＇s method are almost the same when strain softening zone and plastic flow zone are not be considered. Furthermore, it is demonstrated by the other example that dilation angle affects deformation more severely when in-situ stress becomes greater.