MJS桩加固对上覆地铁运营隧道影响研究

以长沙地铁4号线下穿2号线运营隧道MJS水平桩加固工程为背景,对MJS水平桩施工期间周围地层孔压、2号线隧道附加应力、竖向位移进行监测分析,获得MJS水平桩施工对周围地层及运营隧道的影响规律。研究表明:MJS水平桩在钻孔期间,对周边地层孔压及隧道受力变形基本无影响;喷浆期间周围地层孔压增量随距离增加线性减小,隧道附加应力和竖向位移有明显变化,最大分别达到1.8 MPa和5.42 mm,但管片受力变形均处于允许范围内。表明MJS桩施工期间,隧道处于安全状态,研究可为类似工程提供参考。

Study on Influence of MJS Columns Reinforcement on Overpass Subway Operation Tunnel

Based on the Changsha metro line 4 undercrossing the line 2 operating tunnel project with the soil layers between two lines reinforced by MJS horizontal columns, pore-water pressure of surrounding stratum, additional stress and vertical displacement of tunnel were monitored during MJS horizontal columns construction. The influence of MJS horizontal column construction on surrounding stratum and operating tunnels was obtained. The results indicate that the responses of pore-water pressure, additional stress and deformation of the tunnel can be neglected during MJS drilling process. The additional pore pressure decreased linearly with the increasing distance during MJS jet grouting process, meanwhile the additional stress and vertical displacement of the tunnel were obviously changed with the maximum value reached 1.8 MPa and 5.42 mm, respectively. However, the stress and deformation of the segment were less than the allowable values, which indicates that the tunnel is in a safe state during MJS column construction. This study can be a reference for the similar engineering practice.