漫滩二元地层基坑开挖及降水引起的地表沉降预测  

Prediction on Ground Settlement Caused by Foundation Pit Excavation and Dewatering Surrounded by Dual Structural Stratum in Floodplain

作　　者：王涛[1,2] 施斌 王鑫永[3] 邓永锋 WANG Tao;SHI Bin;WANG Xinyong;DENG Yongfeng(School of Earth Science and Engineering,Nanjing University,Nanjing 210093,China;China Design Group Corporation Limited,Nanjing 210014,China;Department of Civil Engineering,Nanjing University of Science and Technology,Nanjing 210094,China;School of Transportation,Southeast University,Nanjing 210096,China)

机构地区：[1]南京大学地球科学与工程学院,江苏南京210093 [2]中设设计集团股份有限公司,江苏南京210014 [3]南京理工大学土木工程系,江苏南京210094 [4]东南大学交通学院,江苏南京210096

出　　处：《防灾减灾工程学报》2020年第5期724-731,共8页Journal of Disaster Prevention and Mitigation Engineering

基　　金：国家重大科研仪器研制项目(41427801);国家自然科学青年基金项目(41502274)资助。

摘　　要：基坑土体开挖及降水引起的地表沉降预测是基坑工程安全领域关键问题之一。工程中常用的基坑支护结构计算软件未考虑降水固结引起的沉降。为全面计算基坑工程引起的地表沉降,提出了理论计算模型,采用MAT-LAB编制差分算法程序,生成附带基坑围护结构及土体分层单元的场地模型,实现了自动计算地下水位下降深度与地表沉降。以位于长江和秦淮河漫滩地区二元结构场地的南京地铁螺塘街站为案例进行验证,该方法计算的地下水位降深和地表沉降与现场监测数据基本吻合,其中观测孔位地下水降深偏差为2.4%~8.6%,地表沉降计算值偏差大都在10%以内,表明了所提计算方法的可靠性。进行泛化分析,将原始二元地层与上部淤泥质土层替换为砂层工况进行比较,分析了围护结构插入比、土层性质对地下水位降深和地表沉降的影响。结果表明:原始二元地层相对于替换砂层的工况,水位降深小但沉降峰值大,对水位下降的反应更加灵敏,沉降曲线曲率更大,对周边环境的危害也更大,围护结构插入比的增加对地表沉降削弱效果显著。In the security field of foundation pit engineering,accurate prediction on ground surface settlement caused by excavation and dewatering is one of the key issues. Most softwares used for designing foundation pit retaining structures do not take settlement caused by dewatering into consideration despite its significance. In order to calculate the settlement caused by foundation pit construction comprehensively,a theoretical model,which applies differential algorithm method programed by MATLAB code,is proposed in this paper. The proposed program can generate enclosure structure and layered soil element,and can calculate automatically the groundwater drop depth and ground settlement.The Luotang Street metro station project is used for validation,which is located in the dual structural stratum of Yangtze River and Qinhuai River floodplain. The values calculated by the proposed program are compared with the on-site monitoring data. The deviation of groundwater drop depth between the calculated and monitoring data is only 2.4%~8.6%. The deviation of ground maximum settlement between the calculated and monitoring data is less than 10%. The above results indicate the reliability of the proposed method and the hereinafter developed program. The comparative analysis between the original dual structural stratum and designed layer conditions that replace upper silt soil with sand is carried out. The influence of enclosure structure’s insertion ratio and soil properties on the groundwater drop depth and ground settlement was analyzed systematically. The results show that,compared with the case of replacing upper silt soil by sand,the groundwater drop depth of the original dual stratum is less,but the peak value of ground settlement is larger,and the original dual stratum is more sensitive to dewatering,and the curvature of ground settlement curve is greater,and it’s more harmful to the surrounding environment. The settlement peak can be more obviously weakened by increase of the insertion ratio.

关 键 词：基坑工程 二元结构地层 地下水 地表沉降 围护结构插入比 

分 类 号：TU43[建筑科学—岩土工程]