圆形巷道围岩应变软化弹塑性分析

 岩土类材料广义上都呈应变软化力学行为，考虑峰后岩石应变软化过程中引起后继强度面收缩的特性，认为岩体在足够小的局部范围内材料特性保持不变，将后继破坏岩体分为多个塑性区，给出基于平面应变和Mohr- Coulomb准则的围岩准应变软化弹塑性应力解析式，并给出符合围岩后继强度和变形演变规律的各软化区半径求解方程组。洞室围岩变形特征曲线是地下工程支护设计的重要依据，考虑岩体破裂过程中变形参数不断劣化的特性，分析剪切模量劣化对围岩变形、软化半径及破裂半径的影响。最后通过算例对模型进行验证，计算结果可以对地下工程的优化支护设计及安全性评价提供理论依据。

ELASTOPLASTIC ANALYSIS OF CIRCULAR OPENINGS IN STRAIN-SOFTENING ROCK MASSES

Geotechnical materials are generally performed with strain-softening mechanical behaviors. Considering post-strength surface shrinkage characters during strain softening process，it is assumed that the rock mass material parameters keep unchangeable in sufficiently small region. In this way，the rock mass is divided into multi-plastic rings after failure. Based on the plane strain condition and Mohr-Coulomb criterion，the quasi-strain softening elastoplastic closed-form expressions are obtained. Considering the rock mass strength evolution law，the multi-plastic radii can also be obtained using rock mass rupture conditions on the adjacent plastic rings. It is generally known that the ground reaction curve(GRC) is a very important basis for the underground lining design. The rock mass deformation parameters are also deteriorated with the increase of plastic deformation. So，the influences of deteriorated degree of shear modulus on rock mass deformation，softening radius and residual radius are analyzed. Finally，the analytical method is validated by an example；and the results can provide meaningful theoretical foundations for underground engineering optimization design and its stability analysis.