基于装配式预应力型钢组合支撑的基坑分层开挖过程模拟分析

Simulation Analysis of Layered Excavation Process of Foundation Pit Based on Support of Prefabricated Prestressed Steel Composite

以黄木岗综合交通枢纽为依托,设计提出了一种装配式预应力型钢组合支撑体系,构建了基坑分层开挖与支护过程的有限元模型,分析了不同工况下基坑、土体与型钢组合支撑的力学特性,验证了型钢组合支撑的稳定可靠性,并探究了不同开挖方式与开挖厚度对支护结构和土体受力特性的影响规律。结果表明:①地连墙的水平位移在基坑深度为4~6 m时达到峰值,整体变形呈“鼓肚型”,且均在安全范围内;②基坑周边地表最大沉降量仅为-2.48 mm,远小于规范限值12 mm,且在基坑开挖3倍坑深的范围之外趋于稳定;③型钢组合支撑以受压为主,最大轴压应力为50 MPa,支撑体系受力合理;④分层开挖厚度2 m方案的地连墙变形、地表沉降峰值以及支撑结构内力均最小,但分层开挖厚度4 m方案的内力与变形增量不大,考虑到施工进度与经济性,因此建议选择分层开挖厚度4 m的方案。

Based on the Huangmugang Comprehensive Transportation Hub,a prefabricated prestressed stel composite support system was designed.A finite element model of the layered excavation and support process of the foundation pit was constructed.The mechanical characteristics of the foundation pit,soil and section steel composite support under different working conditions were analyzed.The stability and reliability of the section steel composite support were verified.The influence of different excavation methods and depth on the support structure and soil stress characteristics was explored.The results show that the horizontal displacement of the diaphragm wall reaches its peak with 4~6 m deep foundation pit.The overall deformation shows a"bulge shaped"within the safe range;The maximum settlement of the surface around the foundation pit is only-2.48 mm,far less than the standard limit of 12 mm,and tends to be stable outside the range of 3 times the depth of the pit excavation;The composite support of section steel is mainly under compression with a maximum axial compressive stress of 50 MPa.The support system is reasonable;All of the deformation of the diaphragm wall,peak value of surface settlement and internal force of the support structure are the smallest of the scheme of 2 m layered excavation.However,the internal force and deformation increment of the 4 m layered excavation scheme are not significant.Considering the construction progress and economy,it is recommended to choose the 4 m layered excavation scheme.