基于Hoek-Brown准则西原模型的圆形隧洞黏弹塑性解

为进行流变围岩圆形隧洞工程应力、应变分析,将Hoek-Brown强度准则引入到西原流变本构模型,同时在力学模型中考虑掌子面推进效应和支护阻力对围岩应力释放率的影响,得到了支护条件下基于Hoek-Brown准则西原模型的圆形隧洞黏弹塑性解。通过锦屏二级水电站引水隧洞案例验证解析方法的可靠性,并进行了塑性区半径和围岩变形的影响因素定量分析。研究结果表明:(1)基于Hoek-Brown准则的西原模型更能反映实际隧洞工程岩体流变特性,建立的解析方法能够考虑围岩应力释放效应和塑性体积扩容特征对围岩变形的影响,其计算结果与实际监测数据吻合良好;(2)围岩应力释放系数、Hoek-Brown准则参数s、原岩应力和隧洞半径对塑性区半径的影响较大,是判断流变围岩隧洞稳定性的主要考虑指标,相对而言,岩石单轴抗压强度和Hoek-Brown准则参数m对塑性区半径的影响较小;(3)引入围岩扩容系数后,围岩位移量显著增加,但基本不影响围岩流变变形曲线形态和塑性区半径,从洞壁向围岩内部延伸,围岩扩容系数对围岩变形的影响越来越小。

Hoek-Brown strength criterion and Nishihara model-based visco-elastoplastic solutions for circular tunnel

Hoek-Brown strength criterion is introduced into Nishihara rheological constitutive model for the analysis made on the stress and strain of the circular tunnel with rheological surrounding rock during its construction，while the impacts from both the advancing effect and the supporting resistance of the excavating face on the releasing rate of the stress of the surrounding rock are considered in the mechanical model； thus the Hoek-Brown strength criterion and Nishihara model-based visco-elastoplastic solutions for circular tunnel under the supporting condition are obtained. Furthermore，the quantitative analyses on the impacting factors of the plastic zone radius and surrounding rock deformation are carried out as well. The study result shows that： （1） Hoek-Brown strength criterion-based Nishihara model can well reflect the rock mass rheological characteristics for the actual construction of tunnel，and its calculation results can better coincide with the actual monitoring data； （2） the impacts from the releasing coefficient of surrounding rock stress，the parameter of Hoek-Brown strength criterion s，the in-situ stress and the radius of tunnel on the radius of the plastic zone are larger； （3） the displacement of surrounding rock significantly increases after the introduction of the surrounding rock dilatancy coefficient，but there is basically no any impacts on the shape of the rheological deformation curve of surrounding rock and the radius of the plastic zone. Meanwhile，the impact from the surrounding rock dilatancy coefficient on the deformation of surrounding rock generally becomes smaller and smaller from the tunnel wall to the inside of surrounding rock.