三面临河浅基岩含流砂地层深基坑地下水综合防控措施研究

Study on Comprehensive Prevention and Control Measures of Groundwater in Deep Foundation Pit with Shallow Bedrock and Quicksand Strata Facing River on Three Sides

为解决三面临河特殊环境条件下浅基岩含流砂地层深基坑开挖过程中的地下水防控技术难题,结合合肥清三冲调蓄池深基坑工程,对基坑特征及基坑场地地层参数进行分析,提出一种"先在基坑上部适当放坡降深、再在基坑周圈连续封闭且与基岩顶面严密结合"的地下水综合防控措施。同时,对深层搅拌桩及高压旋喷桩嵌岩施工、钻孔灌注桩穿越流砂地层钢板护壁护筒施工等关键技术进行阐述。工程实施效果及监测数据表明,基坑坑内降水开挖对周边环境及支护结构影响均在合理范围内,基坑侧壁整体无明显渗漏水情况发生,地下水防控措施防护整体效果良好。

To find the solutions of groundwater prevention and control in deep foundation pit excavation with shallow bedrock and quicksand strata facing river on three sides,the characters and stratum parameters of foundation pit project in Hefei Qingsanchong storage pond are analyzed.A set of comprehensive groundwater prevention and control measures,i.e.,appropriate slope depth in upper part,blocking water around the foundation pit and inserting piles to the top of bedrock is put forward.Meanwhile,key technical points,i.e.,the use of deep mixing pile and high-pressure jet grouting pile in rock-socketed construction,the use of steel plate wall after bored piles crossing quicksand stratum,etc.,are demonstrated.The implementation effect and monitoring data show that the impact of dewatering excavation on surrounding environment and supporting structure is within a reasonable range,and there is no obvious leakage on the side wall of the foundation pit,which proves that the overall effect of groundwater prevention and control measures is good.