地下连续墙受力变形光纤监测与数值模拟研究∗

Fiber Optic Monitoring and Numerical Simulation of Stress and Deformation of Diaphragm Wall

摘要:

地下连续墙是一种常见的深基坑支护方式，具有刚度大、防渗性能好、适应范围广等优点，但其受力变形规律较为复杂。基于超弱光纤光栅感测技术，对某地铁车站基坑地下连续墙水平位移进行实时监测。将监测数据与数值模拟结果进行对比，验证了数值分析模型选取的合理性，并基于该数值分析模型研究了不同厚度软土层中，地下连续墙水平位移的变化规律，通过墙体位移梯度（D_w）和软土位移梯度（D_r ）进行临界厚度比计算。研究结果显示： 水平位移随软土厚度的变化呈“凸肚”状，沿深度方向划分为相对稳定区、线性增长区、最大变形区和线性下降区。 利用 D_w和 D_r标定出临界厚度比为 0.24；土压力变化在基坑前四步开挖过程中较为稳定，而在第五步开挖与施工后 40 d 变化显著。上述研究结果为类似工程的设计、施工和监测方案的制定提供了重要参考。

Abstract:

As a common support method in deep excavation， diaphragm walls have complex stress and deformation regulation， making them a hot research topic in excavations. In this paper， based on the fiber Bragg grating sensing technology， the horizontal displacements of a diaphragm wall of a subway station were measured. The monitoring data was compared with the numerical simulation results， and the rationality of the numerical analysis model was verified. Based on the numerical analysis model， the variation law of the horizontal displacement of the underground diaphragm wall in the soft soil layer of different thicknesses was studied. The critical thickness ratio was calculated by the wall displacement gradient D_w and the soft soil displacement gradient D_r. The results show that the variation of horizontal displacement of the diaphragm wall with the thickness of soft soil is generally in a shape of "convex belly". The deformation of the diaphragm wall can be divided into relatively stable zone， linear growth zone， maximum deformation zone and linear decline zone along the depth direction. The critical thickness ratio α_cr was calibrated as 0.24 using D_w and D_r. The earth pressure is relatively stable in the first four excavation processes， but changes significantly after 40 days of excavation in the fifth excavation process. The research results provide a valuable reference for the design， construction， and monitoring schemes of similar projects.