考虑接头弱化的小直径竖井地下连续墙和钢管桩围护力学性态对比分析

Comparative Analysis on Mechanical Behavior of Diaphragm Wall and Steel Pipe Pile with Small Diameter Shaft Considering Joint Weakening

城市更新背景下基础设施建设过程中,直径15 m左右、挖深25 m以上的小直径超深竖井工程不断涌现。建筑基坑设计一般采用平面弹性抗力分析,未考虑空间效应而导致方案偏保守;采用三维m值法或三维有限元法时,若不考虑围护墙环向刚度弱化则变形也远低于实测。结合实际工程采用三维精细化数值模拟方法,参考已有研究给出的地下连续墙接头单元压缩试验数据,首先对比分析地下连续墙是否考虑接头弱化2种情况,结果表明型钢接头按双面5 mm夹泥考虑接头弱化与实测基本吻合;在此基础上对比分析1.2、1.0、0.8 m三种地下连续墙方案,随地下连续墙厚度降低墙身侧移依次递增约20%,而最大弯矩依次递减约25%,并验证0.8 m厚地下连续墙也能满足设计要求;针对中心城区复杂施工环境提出了基于钢管桩的竖井绿色围护方案,分析表明Ф900 mm、1.3 m间距的钢管桩圆形围护与1.0 m厚圆形地下连续墙围护的力学性态较为接近,满足施工要求。

In the context of urban renewal,small-diameter ultra-deep shaft projects,with diameters around 15 m and excavation depths exceeding 25 m,are becoming increasingly common.The plane elastic resistance method is typically employed for foundation pit design,which does not account for spatial effects,leading to conservative designs.When using the three-dimensional m-value method or three-dimensional finite element method,neglecting the circumferential stiffness weakening of the retaining wall results in deformation far lower than actual measurements.This study adopts a threedimensional refined numerical simulation method,referencing joint compression test data for diaphragm walls from existing research.A comparison is made between two scenarios:one that considers joint weakening and one that does not.Results show that joint weakening with 5 mm mud on both sides of section steel joints closely aligns with actual measurements.Based on this,three diaphragm wall schemes(1.2 m,1.0 m,and 0.8 m)are analyzed.As the diaphragm wall thickness decreases,lateral displacement increases by about 20%,while the maximum bending moment decreases by around 25%.It is confirmed that a 0.8 m thick diaphragm wall can meet design requirements.For complex construction environments in central urban areas,a green enclosure scheme using steel pipe piles for vertical shafts is proposed.The analysis shows that the mechanical behavior of a circular enclosure usingФ900 mm steel pipe piles with 1.3 m spacing is similar to that of a 1.0 m thick circular diaphragm wall,meeting construction requirements.