桩锚复合支护深基坑变形的流固耦合分析

Deformation Analysis of Deep Foundation Pit with Pile-anchor Composite Support Considering Fluid-Solid Coupling

深基坑开挖降水过程中,坑内外压力差可能引起严重的工程事故。本文通过有限元软件MIDAS/GTS,采用渗流应力耦合理论及摩尔库伦模型,结合某桩锚复合支护深基坑工程实例建立三维有限元模型分析了该深基坑工程的变形情况,并与不考虑耦合的基坑变形情况进行对比,主要包括锚杆轴力图、桩剪力图与弯矩图、基坑地表沉降、坑底回弹、侧向位移等。结果表明:在两种不同的有限元模拟条件下基坑变形形态基本一致;总的来说,流固耦合分析引起的基坑变形小于不考虑耦合分析的基坑变形,支护结构的受力变形也较小,更接近实际情况。考虑地下水流固耦合分析对基坑变形的影响不容忽视,对实际工程的设计优化有一定的参考意义。

The pressure difference between the internal and external deep foundation pit may cause serious engineering accidents when the pit is excavated for lowering the water level and pressure. In the paper, a three-dimensional finite element model of the pile-anchor composite deep foundation was established to analyze the deformation of the pit with the fluid-solid coupling theory and Mohr-Coulomb model, and another model without considering fluid-solid coupling was also set up. The calculation results such as the axial force of the anchor, pile shear force and bending moment, settlement of the pit surface, bottom rebound and lateral displacement obtained from the two finite element models were analyzed. The authors think that the deformation of foundation pit which were got from two different finite element simulation methods should be basically consistent. Generally speaking, the pit deformation considering the fluid-solid coupling theory is smaller than that without considering the coupling and the stress and the deformation of support structures is also small, just like the real case. It is concluded that fluid-solid coupling of groundwater should be considered while analyzing the deformation of deep foundation pit, which will be a valuable reference for the design optimization of the excavation.