黄河三角洲地区基坑实例研究

山东东营地区位于黄河三角洲,地下水位高,土质以粉土及粉质粘土为主,基坑施工难度大且施工扰动与降水会引起周边建筑物的不均匀沉降.针对该地区基坑支护的特点和难点,围绕某基坑支护方式、地下水控制、施工难点及变形监测等方面展开研究.结果表明：（1）该区桩锚支护中的锚杆可采用自钻式锚杆,但应采取施工措施保证锚杆注浆充分;（2）基于土层特性,地下水控制只能采用悬挂式止水帷幕,坑内降水井的深度宜小于止水帷幕1～2m,大于坑底深度4m;（3）桩锚支护能有效控制基坑的侧向位移,但因锚杆施工扰动会引起周边建筑物的沉降与不均匀沉降,影响范围约为基坑开挖深度的10倍.

Case study on foundation pit in the Yellow River Delta

Dongying area is located in the Yellow River Delta,where the groundwater level is high and stratum is mainly composed of silt and silty clay.In this area,pit excavation is challenging,for construction disturbance and dewatering would result in differential settlement of the surrounding buildings.To probe into this problem,a case history is studied about its supporting type,groundwater control,construction difficulties and deformation monitoring.The results show：（1） pile-anchor retaining is applicable in which anchor is self-drilled,but construction measures should be taken to ensure the anchor＇s grouting volume ; （2） based on soil characteristics,suspended waterproof curtain can only be used in groundwater control,and the depth of the dewatering wells should be 1-2 m lower than waterproof curtain and 4 m higher than the bottom of the pit; （3） pile-anchor retaining system can effectively control the lateral displacement of foundation pit,but the construction disturbance will cause subsidence and surrounding buildings＇ uneven settlement,affecting a range of about 10 times the depth of excavation.