富水砂层狭长型地铁基坑降水设计及应用研究

Dewatering Design for Long and Narrow Subway Excavation in Water-rich Sand and its Application

富水砂层狭长型地铁基坑工程施工中,降水是其重点考虑问题。依托西安某地铁基坑工程,对比了等间距对称布置和间隔“之”字形布置两种基坑降水方案,利用MIDAS GTS对基坑降水进行数值模拟计算,结合实测数据对比分析,结果表明:针对富水砂层狭长型基坑工程,两种降水方案水位降深均可满足施工要求,采用间隔“之”字形的管井布置方式可以减少降水井数量,基坑开挖过程中地表沉降较小;数值模拟结果显示基坑降水引起的地表沉降较小,地表沉降的改变主要由基坑开挖引起;经现场监测数据进一步验证,地下水位实测值与计算值接近,周边地表沉降符合规范要求。间隔“之”字形管井布置方式可对今后类似狭长型基坑工程降水设计提供参考。

In the construction of long and narrow subway excavation in water-rich sand layers,dewatering is the key issue to be considered.Based on a subway excavation project in Xi'an,two excavation dewatering schemes of equal-spaced symmetrical arrangement and spaced"zigzag"arrangement are compared,and MIDAS GTS is used to carry out numerical simulation calculation of excavation dewatering.Combined with the comparison and analysis of measured data,the results show that:for the long and narrow excavation project in the water-rich sand layer,the water level drawdowns of the two dewatering schemes can both meet the construction requirements.The interval"zigzag"arrangement of tube wells can reduce the number of dewatering wells,and the surface settlement during the excavation of the foundation pit is small;the numerical simulation results show that the surface settlement caused by the dewatering of the excavation is small,and the change of the surface settlement is mainly caused by the excavation of the foundation pit.Further verification by the field monitoring data shows that the measured value of the groundwater level is close to the calculated value,and the surrounding surface settlement meets the specification requirements.The interval"zigzag"arrangement of tube wells can provide a reference for the future dewatering design of similar long and narrow excavation projects.