超深基坑减压降水引发地面沉降的估算及其影响因素分析
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摘要
为了深入认识厚层软土地区超深基坑减压降水引发地面沉降的过程,并为地面沉降防治及基坑工程安全提供技术参考,以上海地区为例,从工程水文地质特性、影响因素、综合分区、沉降估算等方面开展了前瞻性研究.超深基坑减压降水需求估算结果表明,超深基坑减压降水将会涉及更多、更深的承压含水层;在分析总结超深基坑减压降水引发地面沉降的主要影响因素的基础上,进行了综合分区研究;基于数值计算和多元回归分析,提出了距基坑3倍开挖深度处降水目标含水层水位降深值及地面沉降量计算公式,并以上海某在建典型超深基坑工程为例进行了验算应用探讨.
Soft soils with high water content,high porosity ratio,high compressibility,high sensitivity and low strength are widely distributed in the southeastern coastal areas in China,which are very easy to cause land subsidence. With the continuous utilization of underground space in soft soil development area,many foundation pits engineering have been implemented,and the depth of excavation is getting deeper and deeper. The land subsidence caused by dewatering in foundation pit to prevent surge and guarantee construction safety will become more complex. In order to understand the process of land subsidence caused by dewatering of ultra-deep foundation pit and provide technical reference for the land subsidence prevention and engineering safety,therefore a prospective study which took Shanghai as an example has been carried out on the hydrogeological characteristics,influencing factors,comprehensive zoning,subsidence estimation and so on. First,the groundwater level drawdown of several confined aquifers was estimated with the regional hydrogeological characteristics in Shanghai. The estimation results show that dewatering of ultra-deep foundation pit would involve more and deeper aquifers,such as the second and third confined aquifers. With the increase of excavation depth,the groundwater level drawdown increases correspondingly which would exacerbate the impact on the surrounding environment. Second,the main influencing factors of land subsidence caused by dewatering of ultra-deep foundation pit were summarized. The main influencing factors are stratum combination,excavation depth of foundation pit,insertion depth of waterproof curtain into target aquifer,area of foundation pit and shape of foundation pit. With these influencing factors,the study on comprehensive zoning has been conducted. Then,the formula of drawdown and land subsidence at the point of 3 times the depth of foundation pit excavation were proposed based on numerical calculation and multiple regression analysis. The calculation coefficients of different partitions were also fitted out. Finally,a ultra-deep foundation pit in Shanghai was chosen to do some discussion about the study results. The excavation depth of this ultra-deep foundation pit exceeds 40 m,which must consider the influence of second and third confined aquifers.
Soft soils with high water content,high porosity ratio,high compressibility,high sensitivity and low strength are widely distributed in the southeastern coastal areas in China,which are very easy to cause land subsidence. With the continuous utilization of underground space in soft soil development area,many foundation pits engineering have been implemented,and the depth of excavation is getting deeper and deeper. The land subsidence caused by dewatering in foundation pit to prevent surge and guarantee construction safety will become more complex. In order to understand the process of land subsidence caused by dewatering of ultra-deep foundation pit and provide technical reference for the land subsidence prevention and engineering safety,therefore a prospective study which took Shanghai as an example has been carried out on the hydrogeological characteristics,influencing factors,comprehensive zoning,subsidence estimation and so on. First,the groundwater level drawdown of several confined aquifers was estimated with the regional hydrogeological characteristics in Shanghai. The estimation results show that dewatering of ultra-deep foundation pit would involve more and deeper aquifers,such as the second and third confined aquifers. With the increase of excavation depth,the groundwater level drawdown increases correspondingly which would exacerbate the impact on the surrounding environment. Second,the main influencing factors of land subsidence caused by dewatering of ultra-deep foundation pit were summarized. The main influencing factors are stratum combination,excavation depth of foundation pit,insertion depth of waterproof curtain into target aquifer,area of foundation pit and shape of foundation pit. With these influencing factors,the study on comprehensive zoning has been conducted. Then,the formula of drawdown and land subsidence at the point of 3 times the depth of foundation pit excavation were proposed based on numerical calculation and multiple regression analysis. The calculation coefficients of different partitions were also fitted out. Finally,a ultra-deep foundation pit in Shanghai was chosen to do some discussion about the study results. The excavation depth of this ultra-deep foundation pit exceeds 40 m,which must consider the influence of second and third confined aquifers.
引文
[1] Ye S J,Xue Y Q,Wu J C,et al.Progression and mitigation of land subsidence in China.Hydrogeology Journal,2016,24(3):685-693.
[2] 杨天亮,许言.国际地面沉降与城市安全研究动态-第一届国际城市地质学术研讨会综述.上海国土资源,2017,38(2):1-3.(Yang T L,Xu Y.Research trends in international land subsidence and urban security:An overview of the first international symposium on urban geology.Shanghai Land & Resources,2017,38(2):1-3.)
[3] 魏子新,翟刚毅,严学新等.上海城市地质.北京:地质出版社,2010,145-171,192-200.(Wei Z X,Zhai G Y,Yan X X,et al.Shanghai urban geology.Beijing:Geological Publishing House,2010,145-171,192-200.)
[4] 杨天亮,严学新,王寒梅等.基坑施工引发的工程性地面沉降研究.上海地质,2009(2):15-21.(Yang T L,Yan X X,Wang H M,et al.Study on land subsidence induced by excavation engineering.Shanghai Geology,2009(2):5-21.)
[5] 杨天亮,严学新,王寒梅等.水位与沉降双控模式下浅层地下水压力回灌试验研究.上海地质,2010,31(4):12-17.(Yang T L,Yan X X,Wang H M,et al.Experimental research of shallow aquifer pressure groundwater recharge based on dual control pattern of groundwater level and land subsidence.Shanghai Geology,2010,31(4):12-17.)
[6] 杨天亮.深基坑减压降水引发的地面沉降效应分析.上海国土资源,2012,33(3):41-44,70.(Yang T L.Analysis of the land subsidence impact of dewatering of deep foundation pits.Shanghai Land & Resource,2012,33(3):41-44,70.)
[7] 占光辉,何晔,黄鑫磊.上海地铁车站深基坑工程地面沉降防治实例分析.上海国土资源,2013,34(2):68-70.(Zhan G H,He Y,Huang X L.Discuss on land subsidence control for deep foundation pit engineering in Shanghai subway station.Shanghai Land & Resource,2013,34(2):68-70.)
[8] 史玉金,张先林,陈大平.上海深层地下空间开发地质环境条件及适宜性评价.地质调查与研究,2016,39(2):130-135.(Shi Y J,Zhang X L,Chen D P.Geo-environmental condition and feasibility assessment of the deep underground space in Shanghai city.Geological Survey and Research,2016,39(2):130-135.)
[9] 上海市工程建设规范.岩土工程勘察规范.DGJ08-37-2012.(Code for engineering construetion in Shanghai.Code for Investigation of Geotechnical Engineering.DGJ08-37-2012.)
[10] 黄鑫磊,何晔,占光辉.深基坑减压降水设计优化与止水帷幕隔水效应分析.上海国土资源,2014,35(2):25-27,61.(Huang X L,He Y,Zhan G H.Analysis of the optimization of deep-foundation pit dewatering design and the effect of a waterproof curtain.Shanghai Land & Resource,2014,35(2):25-27,61.)
[11] 吴林高,朱雁飞,娄荣祥等.深基坑工程承压水危害综合治理技术.北京:人民交通出版社股份有限公司,2016,27-48.(Wu L G,Zhu Y F,Lou R X,et al.Comprehensive treatment of damages caused by confined water in deep excavation engineering.Beijing:China Communications Press CO.,Ltd,2016,27-48.)
[12] Wang J X,Liu X T,Yang T L.Prevention partition for land subsidence induced by engineering dewatering in Shanghai.Proceedings of the International Association of Hydrological Sciences,372:207-210,DOI:10.5194/piahs-372-207-2015.
[13] 杨天亮.深基坑减压降水地面沉降控制综合分区方法研究.上海国土资源,2018,39(2):64-69,74.(Yang T L.Comprehensive partition method of land subsidence control induced by engineering dewatering of deep fundation pits.Shanghai Land & Resources,2018,39(2):64-69,74.)
[14] Yang T L,Yan X X,Wang H M,et al.Comprehensive experimental study on prevention of land subsidence caused by dewatering in deep foundation pit with hanging waterproof curtain.Proceedings of the International Association of Hydrological Sciences,372:1-5,doi:10.5194/piahs-372-1-2015.
[15] Wang J X,Feng B,Yu H P,et al.Numerical study of dewatering in a large deep foundation pit.Environmental Earth Sciences,2013,69(3):863-872.
[16] 贺小桐,叶淑君,于军等.基于固体颗粒速度场的三维地面沉降模拟.南京大学学报(自然科学),2015,51(6):1268-1278.(He X T,Ye S J,Yu J,et al.Three-dimensional land subsidence modeling based on solid particle velocity.Journal of Nanjing University(Natural Sciences),2015,51(6):1268-1278.)
[2] 杨天亮,许言.国际地面沉降与城市安全研究动态-第一届国际城市地质学术研讨会综述.上海国土资源,2017,38(2):1-3.(Yang T L,Xu Y.Research trends in international land subsidence and urban security:An overview of the first international symposium on urban geology.Shanghai Land & Resources,2017,38(2):1-3.)
[3] 魏子新,翟刚毅,严学新等.上海城市地质.北京:地质出版社,2010,145-171,192-200.(Wei Z X,Zhai G Y,Yan X X,et al.Shanghai urban geology.Beijing:Geological Publishing House,2010,145-171,192-200.)
[4] 杨天亮,严学新,王寒梅等.基坑施工引发的工程性地面沉降研究.上海地质,2009(2):15-21.(Yang T L,Yan X X,Wang H M,et al.Study on land subsidence induced by excavation engineering.Shanghai Geology,2009(2):5-21.)
[5] 杨天亮,严学新,王寒梅等.水位与沉降双控模式下浅层地下水压力回灌试验研究.上海地质,2010,31(4):12-17.(Yang T L,Yan X X,Wang H M,et al.Experimental research of shallow aquifer pressure groundwater recharge based on dual control pattern of groundwater level and land subsidence.Shanghai Geology,2010,31(4):12-17.)
[6] 杨天亮.深基坑减压降水引发的地面沉降效应分析.上海国土资源,2012,33(3):41-44,70.(Yang T L.Analysis of the land subsidence impact of dewatering of deep foundation pits.Shanghai Land & Resource,2012,33(3):41-44,70.)
[7] 占光辉,何晔,黄鑫磊.上海地铁车站深基坑工程地面沉降防治实例分析.上海国土资源,2013,34(2):68-70.(Zhan G H,He Y,Huang X L.Discuss on land subsidence control for deep foundation pit engineering in Shanghai subway station.Shanghai Land & Resource,2013,34(2):68-70.)
[8] 史玉金,张先林,陈大平.上海深层地下空间开发地质环境条件及适宜性评价.地质调查与研究,2016,39(2):130-135.(Shi Y J,Zhang X L,Chen D P.Geo-environmental condition and feasibility assessment of the deep underground space in Shanghai city.Geological Survey and Research,2016,39(2):130-135.)
[9] 上海市工程建设规范.岩土工程勘察规范.DGJ08-37-2012.(Code for engineering construetion in Shanghai.Code for Investigation of Geotechnical Engineering.DGJ08-37-2012.)
[10] 黄鑫磊,何晔,占光辉.深基坑减压降水设计优化与止水帷幕隔水效应分析.上海国土资源,2014,35(2):25-27,61.(Huang X L,He Y,Zhan G H.Analysis of the optimization of deep-foundation pit dewatering design and the effect of a waterproof curtain.Shanghai Land & Resource,2014,35(2):25-27,61.)
[11] 吴林高,朱雁飞,娄荣祥等.深基坑工程承压水危害综合治理技术.北京:人民交通出版社股份有限公司,2016,27-48.(Wu L G,Zhu Y F,Lou R X,et al.Comprehensive treatment of damages caused by confined water in deep excavation engineering.Beijing:China Communications Press CO.,Ltd,2016,27-48.)
[12] Wang J X,Liu X T,Yang T L.Prevention partition for land subsidence induced by engineering dewatering in Shanghai.Proceedings of the International Association of Hydrological Sciences,372:207-210,DOI:10.5194/piahs-372-207-2015.
[13] 杨天亮.深基坑减压降水地面沉降控制综合分区方法研究.上海国土资源,2018,39(2):64-69,74.(Yang T L.Comprehensive partition method of land subsidence control induced by engineering dewatering of deep fundation pits.Shanghai Land & Resources,2018,39(2):64-69,74.)
[14] Yang T L,Yan X X,Wang H M,et al.Comprehensive experimental study on prevention of land subsidence caused by dewatering in deep foundation pit with hanging waterproof curtain.Proceedings of the International Association of Hydrological Sciences,372:1-5,doi:10.5194/piahs-372-1-2015.
[15] Wang J X,Feng B,Yu H P,et al.Numerical study of dewatering in a large deep foundation pit.Environmental Earth Sciences,2013,69(3):863-872.
[16] 贺小桐,叶淑君,于军等.基于固体颗粒速度场的三维地面沉降模拟.南京大学学报(自然科学),2015,51(6):1268-1278.(He X T,Ye S J,Yu J,et al.Three-dimensional land subsidence modeling based on solid particle velocity.Journal of Nanjing University(Natural Sciences),2015,51(6):1268-1278.)