超浅覆土大断面矩形顶管近距离双线施工地表沉降规律及加固效果评价

矩形顶管施工过程中会对周围土体造成扰动，引起地表产生竖向变形。为研究超浅覆土顶管施工过程中的地表沉降规律，以深圳市某下穿道路矩形顶管工程为背景，使用PLAXIS 3D软件对顶管双线施工进行有限元模拟。首先将模拟结果与实测结果对比以验证模拟结果的合理性，然后分析双线施工地表沉降变化规律，最后对现场加固措施进行评价。主要结论如下：未加固时顶管顶进过程中，最大沉降量位于始发端，最大隆起量位于接收端；加固后地表沉降最大值点及沉降最大值均发生了改变：加固后地表最大沉降值点由始发井改变为顶管中部区域，最大沉降值减少了6.15 mm，表明现场加固方案效果显著；未加固和加固后地表沉降纵向曲线规律基本一致，表现为三个阶段：隆起期、快速沉降期和沉降稳定期；未加固和加固后地表横向沉降槽变化情况基本一致。

Evaluation of surface settlement rule and reinforcement effect in construction of short distance double line of rectangular pipe jacking with large section of ultra-shallow soil cover

The rectangular pipe jacking construction process will cause disturbance to the surrounding soil, causing vertical deformation of the ground surface. To study the surface settlement pattern during the construction of pipe jacking with ultra-shallow overburden, this work conducted finite element simulation of pipe jacking double-lane construction using PLAXIS 3D software with the background of a rectangular pipe jacking project under a road in Shenzhen City. Firstly, the simulation results were compared with the measured results to verify the reasonableness of the simulation results, and then the change pattern of surface settlement rules in the construction of the double line were analyzed, and finally the on-site reinforcement measures were evaluated. The results show that the maximum settlement was at the originating end and the maximum bulge was at the receiving end of the pipe jacking process when the pipe was not reinforced. The maximum point of surface settlement and the maximum settlement value have been changed after reinforcement. The maximum settlement point has been changed from the starting well to the middle of the pipe jacking area, and the maximum settlement value has been reduced by 6.15 mm, which indicates that the on-site reinforcement program has a significant effect. Unreinforced and reinforced surface settlement longitudinal curves are basically the same, showing three phases: uplift, rapid settlement and settlement stabilization. The changes in the lateral surface settlement troughs are generally consistent between the unreinforced and reinforced surfaces.