富水砂性地层地铁深基坑监测及变形分析

Analysis on monitoring and deformation of subway deep foundation pit in water-rich sand stratum

以富水砂性地层顺作法地铁车站基坑为工程背景,结合施工现场监测数据,对围护结构侧向位移变形、周边地表沉降、地下水水位变化及周边建筑物沉降进行分析,总结富水砂性地层的变形性状和对周边环境的影响。监测数据和分析结果表明:富水砂性地层条件下,地下连续墙最大侧向位移δhm的变化范围为0.045%H~0.5%H,均值约为0.22%H,发生位置在(H-4,H+10)之间;基坑开挖引起的地表沉降影响范围在35m以内,约2倍基坑开挖深度;墙后地表最大沉降发生在距离基坑5~10m左右;富水砂性地层有着地下水位高,渗透性强的特点,施工中采用疏干降水与承压降水相结合的措施可以有效控制地下水位变化;施工建设过程中对周边建筑物进行实时监测来反馈指导施工,可以保证施工对周边建筑物的影响在可控范围内。

Taking the foundation pit of subway station with water-rich sand stratum as the engineering background,combined with the monitoring data on the construction site,the lateral displacement deformation of the enclosure structure,the surrounding surface settlement,the groundwater level change and the settlement of surrounding buildings were analyzed to summarize the deformation behavior of the water-rich sand stratum and its impact on the surrounding environment.The monitoring data and analysis results show that:under the conditions of water-rich sand stratum,the maximum lateral displacementδhm of the diaphragm wall ranges from 0.045%H to 0.5%H,with an average value of about 0.22%H,and the occurrence is between(H-4,H+10).The impact of surface settlement caused by excavation of foundation pit ranges within 35m,about 2 times the excavation depth of the foundation pit.The maximum settlement of the surface behind the wall occurs at a distance of about 5~10m from the foundation pit.The water-rich sandy stratum has the characteristics of high groundwater level and strong permeability,and the combination of pumping in phreatic and confined aquifers can effectively control the change of groundwater level in construction;real-time monitoring of surrounding buildings during construction can guide construction,which ensures that the impact of construction on surrounding buildings is within a controllable range.