松散地层隧道进洞段管棚注浆加固效应分析

依托江西萍莲高速莲花隧道,建立考虑松散地层隧道进洞段管棚注浆加固效应的隧道开挖三维有限元计算模型,实现不同管棚注浆加固参数对隧道开挖稳定性影响的定量分析,在数值计算过程中研究注浆加固区力学参数(弹性模量、黏聚力)、管棚间距、注浆半径等因素对隧道稳定性的影响,并将研究成果应用于依托工程中,验证数值计算结果的正确性。研究结果表明:在隧道进洞段,隧道拱顶区域与掌子面前下方区域存在塑性区,上述2个区域为隧道进洞开挖过程中最易失稳的区域;管棚注浆加固可有效限制围岩变形,降低围岩体积应变,且管棚注浆加固区可有效隔离拱顶区域的围岩塑性区,有利于保证隧道拱顶安全;在整个管棚注浆加固长度内,管棚最大沉降量出现在隧道开挖掌子面附近;管棚最大沉降量的绝对值与注浆加固区弹性模量及注浆半径负相关,而与管棚间距正相关,但管棚间距对管棚最大沉降量的影响程度相比其他2个因素小。

Analysis of pipe roof grouting reinforcement effect at tunnel entrance in loose stratum

Based on Lianhua Tunnel in Pinglian Express Way, three-dimensional calculation model was established to study excavation stability considering pipe roof grouting reinforcement effect. Effect of different pipe roof grouting parameters on excavation stability was analyzed quantitatively, such as mechanical parameters of grouted body, pipe roof interval, grouting radius. In the end, numerical simulation results were used and verified in engineering project. Research results showed that there existed plastic failure zone at vault and region below tunnel face. Pipe roof grouting method had effect on limiting deformation of surrounding rock, reducing volume strain of surrounding rock and cutting off connection between plastic failure zone on vault and tunnel. In whole affected area of pipe roof grouting, maximum settlement of pipe roof settlement appeared around tunnel face. Maximum settlement of pipe roof settlement was negatively related with elastic modulus of grouted body and grouting radius, positively related with pipe roof interval. However, influence level of pipe roof interval was lower than elastic modulus of grouted body or grouting radius.