南京浦口某软土基坑险情分析与处理

Analysis and Treatment of the Dangerous Situation of a Soft Soil Excavation Pit in Pukou,Nanjing

南京浦口某典型软土基坑,采用悬臂钻孔灌注桩结合坑外双轴水泥土搅拌桩止水帷幕的支护型式。基坑开挖前支护桩已施工,但后期建筑结构进行了调整,使得基坑加深1.0m。由于抢工期,未进行基坑加固便开始挖土,开挖过程也未采取分段开挖,导致支护桩倾覆,基坑出现险情,坑边路面下沉、坍塌。通过对比原设计与实际开挖2种条件下土压力、支护桩的内力、基坑变形及地面沉降的变化,阐述了险情产生的原因。根据现场情况提出了处理措施,保证基坑的后续施工,同时给出了类似基坑工程的设计、施工和管理方面引以为鉴的建议。

The supporting structure of a typical soft clay foundation pit in Pukou ,Nanjing is consist of cast-in-place bored piles constructed by using cantilevers and the impermeable curtain made of biaxial soil-cement piles outside of the pit .The construction of the supporting piles had been completed before the excavation .However ,the subsequent con-struction was adjusted which added 1 m to the depth of the foundation pit .Meanwhile ,due to the rushing of the construc-tion ,the supporting structure of the pit was not reinforced before the excavation ,and excavation process was not con-structed by stagess .These misconducts led to the overturning of the supporting structure ,as well as the settlement and subsidence of the road surface around the pit .According to the comparison of the soil pressure ,the internal force of the supporting piles ,the deformation of the foundation pit and the ground settlement in the original design and the actual ex-cavation ,the causes of the dangerous circumstances were explained and analyzed .The treatment measures were proposed for the subsequent construction of the pit based on the situation ,meanwhile the suggestion about design ,construction and management of the similar foundation pits were put forward for future references .