旋喷加固淤泥层近距离交叠隧道施工扰动分析

Disturbance Analysis on Stratum and Existing Tunnel below by Shield Tunnel Construction in Reinforced Mud Stratum

基于深圳地铁5号线盾构上穿既有11号线实测数据,研究了旋喷注浆加固淤泥层内新建隧道近距离、小角度上穿既有隧道引起的地表沉降、既有隧道竖向位移和变形规律。研究结果表明:采用本研究旋喷桩加固方案,可以较好地控制隧道开挖过程中的环境扰动,成功地将盾构施工过程中的地表沉降控制在6 mm内,下方临近既有隧道上浮量控制在3 mm内,收敛绝对值控制在3.5 mm内;土压力比(土仓压力和盾构轴线所在位置静止土压力的比值)与盾构前方一定范围内的地表沉降存在显著相关性,当土压力比维持在约1.5时,地表的隆沉不明显;隧道近距离斜交上穿施工引起的下方临近既有隧道产生上浮,上浮影响区域约为开挖线隧道外径的2.5~3.3倍;斜交还引发既有线隧道“斜鸭蛋”变形趋势,“斜鸭蛋”长轴向土体损失区域偏转;双线隧道上穿,引起既有隧道交叠区段的隆沉、竖向、水平向变形过程包含挤压变形、快速发展Ⅰ、趋于稳定Ⅰ、快速发展Ⅱ和趋于稳定Ⅱ这5个阶段。

Field measurements are conducted during the excavation of Shenzhen Metro Line 5 crossing above the existing Shenzhen Metro Line 11. Based on the stratum condition of jet grouting reinforced mud and the working condition of the newly constructed tunnel crossing above the existing tunnel with close distance and small angle, the ground surface settlement, the vertical displacement and structure deformation of Metro Line 11 are analyzed. The results indicate that: the jet grouting reinforcement scheme in this study is quite effective to control the construction disturbance of tunnel excavation;the induced ground surface settlement is smaller than 6 mm, and the cumulative vertical displacement and convergence of the existing tunnel are smaller than 3 mm and 3.5 mm, respectively;the ground settlement within a certain range before the shield machine is directly related to the ratio of earth pressure in chamber to earth pressure at rest at tunnel axis level,and the ground settlement during the stage is small when the ratio is controlled around 1.5;the tunnel excavation crossing above leads to the uplift and deformation of the existing tunnel beneath,and the affected range is around 2.5~3.3 times of the outer diameter of excavated tunnel;Skew intersecting can lead to the deformed tunnel lining like a duck egg standing on end while its’ long axis points to the excavation area;the vertical displacement and the convergence of the existing tunnel go through five stages,which include extrusion deformation,rapid development Ⅰ,slow development,rapid development Ⅱ and stabilizing.