高地应力下层理对层状软岩隧道稳定影响研究

Influence of Bedding on Stability of Layered Soft Rock Tunnel Under High Geostress

西部地区深埋长大隧道由于地应力高、软弱互层围岩等特殊地质条件使隧道的开挖容易产生大变形,给施工造成很大困难。以甘肃尖山隧道高地应力互层软岩段施工为背景,采用离散元软件3DEC对不同层理特征条件下隧道稳定性进行分析。研究结果表明:①互层软岩层理的切割作用越强烈,围岩的自稳能力越差,围岩变形越大,支护受力越大,隧道越不稳定;②随着层理倾角趋于水平或者垂直,围岩的变形与支护结构内力分布趋于对称,支护结构受力更加合理;③层理黏聚力较低时,提高层理黏聚力,对围岩的稳定性起到的提高作用有限;④随着层理摩擦角的提高,对围岩最大变形的影响并不明显。

Due to the special geological conditions such as high geostress and weak interbedded surrounding rock,the excavation of deep buried long tunnels in Western China is prone to large deformation,which makes the construction very difficult.In the context of the construction of high geostress interbedded soft rock section of Jianshan Tunnel in Gansu Province,the discrete element software 3DEC is adopted to analyze the tunnel stability under different bedding characteristics.The results show that:(1)the stronger the cutting effect of interbedded soft rock bedding,the worse the self-stability of surrounding rock,the greater the deformation of surrounding rock,the greater the supporting force,and the more unstable the tunnel;(2)with the bedding angle tending to be horizontal or vertical,the deformation of surrounding rock and the distribution of internal force of supporting structure tend to be symmetrical,and the stress of supporting structure is more reasonable;(3)when the cohesion of bedding is low,the increase of cohesion of bedding has a limited improvement effect on the stability of surrounding rock;(4)with the increase of bedding friction angle,the influence on the maximum deformation of surrounding rock is not obvious.