软土地区地连墙与回灌井相互影响研究

针对地连墙缺口或缺陷问题,基于地铁车站基坑现场回灌试验,结合数值模拟,探究不同工况下地连墙与回灌井的相互影响作用。通过分析天津地铁6号线某车站基坑工程开挖前的抽灌试验,并采用有限差分法对不同地连墙缺口长度、不同回灌井距地连墙缺口距离工况下基坑外采取回灌控制水位下降的效果进行分析评价。结果表明:地连墙缺口长度对回灌效果影响较大,在缺口长度为5 m时,回灌引起的水位抬升效果相对完整墙降低可达50%左右; 基坑降水工程应保证地连墙质量,施工前开展抽灌试验,确保地连墙闭合; 在地连墙长度方向上,回灌井距离地连墙缺口或缺陷10 m以上时,缺口对回灌效果影响相对较小,在利用回灌控制坑外建筑物沉降时,应确保回灌井10 m范围内地连墙截水效果; 回灌井位于基坑外16 m以内时,因地连墙缺口引发的回灌效果差异显著; 距离超过24 m后,缺口对回灌的影响不明显; 实际工程中,回灌井应尽量远离基坑,靠近保护点的位置,避免受到地连墙渗漏影响。

Research on Interaction Between Diaphragm Wall and Recharge Well in Soft Soil Area

Aiming at the gap or defect of diaphragm wall, based on the field recharge test of foundation pit of subway station, combined with numerical simulation, the interaction between diaphragm wall and recharge well under different working conditions were explored. Through the analysis of pumping and grouting test before foundation pit excavation of a station of Tianjin Metro Line 6, the finite difference method was used to analyze and evaluate the effect of recharge outside the foundation pit to control the decline of water level under the conditions of different length of diaphragm wall gap and different distance between recharge well and diaphragm wall gap. The results show that the gap length of diaphragm wall has a great impact on the effect of recharge. When the gap length is 5 m, the water level rise effect caused by recharge is reduced by about 50% compared with the complete wall. The foundation pit dewatering project shall ensure the quality of the diaphragm wall, and the pumping and grouting test shall be carried out before construction to ensure the closure of the diaphragm wall. In the length direction of the diaphragm wall, when the recharge well is more than 10 m away from the gap or defect of the diaphragm wall, the gap has relatively little impact on the recharge effect. When using recharge to control the settlement of buildings and structures outside the pit, the water interception effect of connecting wall within 10 m of recharge well shall be ensured. When the recharge well is located within 16 m outside the foundation pit, the recharge effect caused by the gap of the diaphragm wall is significantly different, and when the distance exceeds 24 m, the impact of gap on recharge is not obvious. In the actual project, the recharge well shall be as far away from the foundation pit as possible and close to the protection point to avoid being affected by the leakage of the diaphragm wall.