随着城市地下空间的发展,作为软土深基坑工程重要围护结构的地下连续墙应用也越来越深,最大深度已超过100 m。超深地下连续墙施工对土体的变形影响成为施工控制关键之一,目前对施工全过程土体位移影响的时空分析以及不同成槽工艺的影响分析还较少。基于此,本文结合两组不同深度(50 m和70 m)地下连续墙采用不同施工工艺(抓斗成槽、抓铣结合成槽)的现场试验,分析了施工全过程对土体位移的时空影响。实测表明,地下连续墙施工期间土体位移经历了“成槽期缓慢发展、静置期快速发展、浇筑期少量恢复”三个阶段;槽段静置期间土体位移增长较快,位移增量约1~3倍,尽快完成混凝土浇筑有利于土体变形控制;混凝土浇筑期间水平位移的恢复量相比地面沉降明显;最终单幅墙施工引起的地面沉降和土体水平位移均未超过10 mm;铣槽机成槽对土体位移的影响与抓斗成槽有显著差别,铣削过程中产生挤土;地下连续墙每幅槽段施工对紧邻的土体影响较显著,对远离的区域影响较小,墙幅连续施工有一定叠加影响但不显著。研究成果可为超深地下连续墙施工影响的量化评估提供参考。

With the development of urban underground space to large depth, the application of diaphragm wall as the preferred enclosure structure of soft soil deep excavation is becoming deeper and deeper, and the maximum depth has exceeded 100 m. The influence of ultra-deep diaphragm wall construction on soil deformation has become one of the key factors in construction control. At present, the spatio-temporal analysis of soil displacement in the whole construction process and the influence analysis of different trenching processes are few. Based on this, this paper carried out two sets of field tests of diaphragm walls with different depth (50 m and 70 m) using different construction techniques (grab-bucket trenching, grab-hydromill combined trenching), and analyzed the spatio-temporal influence of the whole construction process on soil displacement. The measured results show that the soil displacement during the construction of the diaphragm wall has experienced three stages: “slow development in the trench period, rapid development in the static period, and a small recovery in the pouring period”. During the static period of the panel trench, the soil displacement increases rapidly, and the displacement increment is about 1~3 times, so the finish concrete pouring as soon as possible is conducive to soil deformation control. The recovery of horizontal displacement during concrete pouring is more obvious than that of ground settlement. After concrete pouring, the maximum ground settlement and soil horizontal displacement caused by single diaphragm wall construction did not exceed 10 mm. The influence of hydromill on soil displacement is significantly different from that of grab bucket, and soil squeezing occurs during milling. The construction of each section of the diaphragm wall has a significant effect on the soil adjacent to it, and a small effect on the area far away. The continuous construction of the diaphragm wall has a certain superposition effect on the soil deformation but not significant. The test results can provide reference for the quantitative evaluation of the influence of underground diaphragm wall construction on soil.