降雨入渗对防军隧道浅埋小净距段围岩稳定性的影响

Effect of Rainfall Infiltration on Stability of Surrounding Rock in Shallow Buried Small Clear Distance Section of Fangjun Tunnel

为控制降雨入渗对浅埋小净距隧道围岩稳定性的影响,以义东高速公路防军隧道为依托,基于流固耦合理论和水土特征曲线,采用MIDAS GTS NX有限元软件建立浅埋小净距隧道数值模型,对雨季施工时的土体孔隙水压力、围岩变形特征和边仰坡安全系数展开分析。结果表明:随着降雨入渗的持续,围岩及边仰坡土体基质吸力逐渐减小,其土体抗剪强度也随之降低,稳定性变差。经过7 d累积降雨,孔隙水压力增大趋势逐渐放缓,围岩变形达到最大值,工况1的拱顶沉降增大了21.48%,且边仰坡安全系数小于1,处于失稳状态。洞口段采取加固和排水措施来控制围岩的稳定性,边仰坡的安全系数较加固前提升了17.27%,取得了良好的效果,保证了隧道后期的安全施工。

In order to control the influence of rainfall infiltration on the stability of surrounding rock of shallow buried small clear distance tunnel,relying on the Fangjun tunnel of the Yidong expressway,based on the fluid-solid coupling theory and the water-soil characteristic curve,the MIDAS GTS NX finite element software was used to establish a numerical model of a shallow buried small clear distance tunnel to analyze the soil pore water pressure,surrounding rock deformation characteristics and safety factors of side slopes were analyzed during construction in the rainy season.The results show that with rainfall infiltration continues,the matrix suction of the surrounding rock and slope soil gradually decreases,the shear strength of the soil also decreases,and the stability becomes worse.After 7 d of accumulated rainfall,the increase in pore water pressure gradually slows down,and the surrounding rock deformation reaches the maximum.The vault settlement in working condition 1 has increased by 21.48%,and the safety factor of the side slope is less than 1,indicating an unstable condition.Reinforcement and drainage measures are taken to control the stability of the surrounding rock at the tunnel entrance section,the safety factor of the side slope has increased by 17.27%compared with before reinforcement.The site has achieved good results,ensuring the safety of the tunnel's later construction.