大断面隧道软弱围岩-支护系统稳定性分析

Analysis of the Stability of the Support System of Large Section Tunnel in Soft and Weak Surrounding Rock

采用室内试验研究手段获得隧道围岩力学特性,以Mohr-Coulomb弹塑性模型及应变软化模型为基础,采用FLAC3D数值模拟软件,构建三维数值模型,计算深埋隧道围岩特征曲线及纵剖面变形曲线,并对隧道围岩及支护结构安全性进行评价。结果表明:采用弹塑性模型计算所得的隧道围岩安全系数低于应变软化模型所得的安全系数,表明采用弹塑性模型进行支护结构设计时,支护结构安全性较低,设计中可能会增加支护材料费用,而考虑应变软化条件下的围岩安全系数更加接近于工程实际;采用极限应变值或支护结构极限承载压力所获得的围岩—支护系统安全系数较为接近,说明两种方法的差异较小,均可用于隧道围岩支护结构优化设计,采用收敛—约束法计算隧道安全稳定性更加直观,对工程实际具有一定指导作用。

The mechanical characteristics of surrounding rock of tunnel is obtained by indoor experiment research method.Taking the Mohr-Coulomb elastic-plastic model and strain softening model as the foundation and using the FLAC3 Dnumerical simulation software,we construct the three-dimensional numerical model and calculate the characteristic curve of surrounding rock in deep buried tunnel and deformation curve and longitudinal profile,and the safety of tunnel surrounding rock and supporting structure is evaluated.The research results show that the safety factor of tunnel surrounding rock of elastoplastic model is lower than the calculated strain softening model.Using the elastoplastic model for the design of supporting structure,the safety of supporting structure is low.In the design the supporting materials costs may increase.While taking into account the strain softening condition,the safety coefficient of surrounding rock will be close to the engineering practice.Using the limit strain of surrounding rock support system pressure obtained safety coefficient is coincidental.The two methods can be used with minor differences for surrounding rock of the tunnel and support structure optimization design.Calculation of tunnel safety factor uses convergence-confined method,this has certain guiding significance for engineering practice.