考虑时间影响的桩锚支护深基坑流固耦合分析

以深圳地区某桩锚支护深基坑为依托,基于有限元软件PLAXIS的土体硬化(hardening soil,HS)模型对深基坑降水开挖过程进行数值计算,得出降水开挖过程中变形随时间变化的规律,并在考虑时间变化的前提下,分析了考虑流固耦合与不考虑流固耦合深基坑变形和支护结构内力计算结果.研究结果表明:①桩体水平位移和坑外地表沉降在开挖后设置的固结期产生了回弹现象,而固结期后的坑底隆起量相对于开挖后有所增长;②考虑流固耦合与未考虑流固耦合时相比,最终桩体水平位移和坑外地表沉降都明显增大,坑底隆起明显减小,降水对桩体竖向位移和对坑底土体变形有类似的影响规律,并且桩体对坑底隆起具有限制作用;③坑底以上的桩身弯矩,考虑流固耦合时更大,而坑底以下部分恰好相反;另外,考虑流固耦合时的最终轴力小于不考虑流固耦合时的最终轴力.

Fluid structure coupling analysis of deep foundation pit supported by pile anchor consindering time influnce

Based on a deep foundation pit supported by piles and anchors in Shenzhen, the HS model of PLAXIS software was used to calculate the dewatering excavation process of deep foundation pit, and the law of deformation changing with time in dewatering excavation process was obtained. On the premise of considering time change, the calculation results of deformation and internal force of supporting structure of deep foundation pit with and without considering fluid structure coupling were analyzed. The results show that: (1) the horizontal displacement of the pile and the surface settlement outside the pit produce a rebound phenomenon during the consolidation period set after the excavation, and the pit bottom uplift after the consolidation period increases compared with that after the excavation; (2) the horizontal displacement of the pile and the settlement of the ground surface of the outside pit increase significantly when considering the fluid solid coupling compared with that without considering the fluid solid coupling. The vertical displacement of the pile has the same effect on the deformation of the soil at the bottom of the pit, and the pile has a limiting effect on the uplift at the bottom of the pit; (3) the bending moment of the pile above the bottom of the pit is larger when considering the fluid structure coupling, while the part below the bottom of the pit is just the opposite; in addition, the final axial force when considering the fluid structure coupling is smaller than the final axial force when not considering the fluid structure coupling.