变质软岩区小净距隧道合理净距的探讨

Discussion on the Reasonable Spacing of Neighborhood Tunnel in Metamorphic Soft Rock

以某小净距隧道工程为例,针对变质软岩强度低、可塑性强、围岩受力状态复杂且易出现较大塑性圈等特点,引入基于Mohr-Coulomb剪切屈服和拉伸屈服准则的屈服接近度函数,选取该隧道V级围岩隧道埋深30m条件下,对不同隧道净距的围岩应力、屈服接近度、收敛变形进行了数值模拟计算。结果表明,净距越小,中夹岩柱表现越敏感,且围岩应力、屈服接近度、收敛变形值与隧道净距呈非线性关系,并在某个净距值时发生突变后,随着净距增大,各项指标值均趋于缓和。最后提出各项指标值发生突变时的净距作为小净距隧道的合理净距。

By taking a neighborhood tunnel as an example,aiming at the characteristics of soft rock with low strength,high plasticity,complex stress state of surrounding rock,and large plastic circle,and the yield approach index(YAI)function on the basis of Mohr-Coulomb shear yield criterion and tensile yield criterion is introduced.The tunnel surrounding rock stress,yield approaching degree and convergence deformation of different tunnel clear distance are simulated and calculated under the condition of 30 m buried depth of the tunnel.The results indicate that the smaller the spacing is,the more active the folder rock is,in addition,the relationship between the stress of surrounding rock,the yield approaching,the convergence deformation value and the different spacing between tunnel is nonlinear,and when the value of a certain distance is changed,with the increase of the spacing between tunnel,each index value tends to be stable.Finally,it is suggested that the reasonable spacing of neighborhood tunnel is the distance when each index value suddenly reduces.