基于强度折减法的浅埋偏压小净距隧道围岩稳定性分析

针对广东某浅埋偏压小净距高速公路隧道,采用有限元强度折减法基本原理,研究隧道施工过程中各施工工序的安全系数动态变化过程,并对极限状态下关键施工工序的围岩塑性区与隧道围岩位移进行分析,结论为:隧道左洞第一步开挖时,由于中岩柱的出现,其安全系数最小,为最危险施工步,其次为两个洞室临时岩柱上台阶开挖;施工中中岩柱、洞室左拱腰和右拱脚出现大量塑性区,为围岩应力危险区域;中岩柱水平位移在施工过程中呈现出左右往返变化,右侧隧道竖向位移及其上部地表沉降较大,为监控量测重点部位。

Analysis on Surrounding Rock Stability of Shallowly-buried Eccentrically-loaded Tunnels with Small Interval Based on Strength Reduction Method

For the shallowly-buried eccentrically-loaded tunnels with small interval on an express highway in Guangdong province,the basic principle of finite element strength reduction method was employed in this study. Further,the dynamic change process of the safety coefficient of every construction procedure during tunnel construction was researched,and then the plastic zones and the displacements of tunnel surrounding rocks at the important construction procedures under ultimate limited state were analyzed. The research conclusions are as follows:( a) The first excavation procedure of the left tunnel is the most dangerous construction procedure,because its safety coefficient is the smallest one due to the emerging of the middle rock pillar; followed by the top bench excavation of the temporary rock pillar between the two tunnels.( b) During construction,a lot of plastic zones will occur at the middle rock pillar and at the tunnel's haunch and arch springing,so these zones are the dangerous stress zones of surrounding rock.( c) During construction,the horizontal displacement of middle rock pillar will change from side to side, while the vertical displacement of the right tunnel and upper ground surface settlement are relatively larger; therefore these parts should be regarded as the key parts in the process of monitoring and measurement.