复杂地质条件下某深大基坑降水方案优化设计
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摘要
某深大基坑位于长江下游岸边,场地地层为典型的二元结构,基坑开挖涉及的两层承压含水层间的弱透水层局部缺失,之间水力联系密切,基坑场地地质条件极为复杂,基坑施工降水直接关系到基坑工程的安全。这里将基坑分3个区,分别进行降水设计。具体降水方案:Ⅰ区两层承压含水层和Ⅱ区第一承压含水层被围护结构隔断内外水力联系,采用疏干井降水;Ⅱ区第二承压含水层未被围护结构隔断,Ⅲ区两层承压含水层水力联系密切,针对这两个区域设计了两套降水方案,方案一在Ⅱ区和Ⅲ区均布置有降水井,在Ⅱ区对第二承压含水层降水,在Ⅲ区对第一承压含水层降水;方案二仅在Ⅲ区布置降水井对第一承压含水层降水。为了更好地对降水方案进行对比分析,验证方案的可行性,对此进行了数值模拟分析,计算结果显示,两种方案均能满足降水要求,不过方案二布井数量少,基坑外水位降深较小,对周边环境影响更小,优于方案一。
A large deep foundation pit,located on the bank of lower reaches of Yangtze River,is of a typical dual structural stratum. An impermeable layer between two confined aquifers involved in the pit excavation is partial loss so that the two confined aquifers have a very close hydraulic connection. Because the condition of the formation under the pit site is very complex,and foundation pit dewatering has a direct influence on the safety of foundation pit engineering. The pit is divided into three zones for separate dewatering design. Here is the detailed plan. The hydraulic connection to the outside is cut off by the retaining structure in the two confined aquifers at Region Ⅰ and the first confined aquifer at zone Ⅱ. Unwatering wells are used in these layers. The second confined aquifer in zoneⅡ is not cut off,and the two confined aquifers in zone Ⅲ where the impermeable layer is lost,have a close hydraulic connection. Two dewatering schemes are designed for these two regions. In scheme 1,wells are set in zoneⅡ to pump the groundwater of the second confined aquifer,and in zone Ⅲ to pump the groundwater of the first aquifer. However,in scheme 2,wells are only set in zone Ⅲ and pump the groundwater of the first aquifer. For a better comparison between the two schemes and verifying their feasibility,a numerical simulation is conducted. The results show that both of the schemes are feasible and can lower the groundwater level to 1m below the bottom of the foundation pit. So the two schemes can both meet the requirement of dewatering. But scheme 2 needs less wells and results in smaller water table decline of aquifers outside the foundation pit,so that it has less impact on the environment surroundings,and it's more suitable than scheme 1.
A large deep foundation pit,located on the bank of lower reaches of Yangtze River,is of a typical dual structural stratum. An impermeable layer between two confined aquifers involved in the pit excavation is partial loss so that the two confined aquifers have a very close hydraulic connection. Because the condition of the formation under the pit site is very complex,and foundation pit dewatering has a direct influence on the safety of foundation pit engineering. The pit is divided into three zones for separate dewatering design. Here is the detailed plan. The hydraulic connection to the outside is cut off by the retaining structure in the two confined aquifers at Region Ⅰ and the first confined aquifer at zone Ⅱ. Unwatering wells are used in these layers. The second confined aquifer in zoneⅡ is not cut off,and the two confined aquifers in zone Ⅲ where the impermeable layer is lost,have a close hydraulic connection. Two dewatering schemes are designed for these two regions. In scheme 1,wells are set in zoneⅡ to pump the groundwater of the second confined aquifer,and in zone Ⅲ to pump the groundwater of the first aquifer. However,in scheme 2,wells are only set in zone Ⅲ and pump the groundwater of the first aquifer. For a better comparison between the two schemes and verifying their feasibility,a numerical simulation is conducted. The results show that both of the schemes are feasible and can lower the groundwater level to 1m below the bottom of the foundation pit. So the two schemes can both meet the requirement of dewatering. But scheme 2 needs less wells and results in smaller water table decline of aquifers outside the foundation pit,so that it has less impact on the environment surroundings,and it's more suitable than scheme 1.
引文
Cui Y G.2015.Multi-well effect of ultra-large foundation pit in deep thick and highly permeable aquifers[J].Journal of Engineerin Geology,23(3):574~579.
Li X K,Che X G,Tan L,et al.2015.Dewatering construction technolog of deep and soft foundation excavation in No.9 building of Jinwan Plaza[J].Construction Technology,44(1):21~24,93.
Li Y,He Z Z,Yan G H,et al.2012.Excavation dewatering and ground subsidence in dual structural stratum of Wuhan[J].Chinese Journa of Geotechnical Engineering,34(S1):767~772.
Liu G B,Wang H X.2002.Influence of the pressure water in shallow silt sand in Shanghai on excavation[J].Chinese Journal of Geotechnica Engineering,24(6):790~792.
Luo L F,Zhang L H,Yang S,et al.2008.Study on permeability o cohesionless coarse-grained soil[J].Yunnan Water Power,24(1):22~24.
Luo Z J,Li L,Cao H B,et al.2006.Numerical simulation of threedimensional seepage field of a deep foundation pit during dewaterin in a complex composite aquifer system---case study of dewaterin of a pit at the Shanghai Finance Center[J].Journal of Engineerin Geology,14(1):72~77.
Luo Z J,Zhang Y P,Liu J B.2007.Three-dimensional seepage numerica simulation of deep foundation pit dewatering in complicated quaternary loose sediments with great thickness-a case study o dewatering reconstructed foundation pit at Dongjiadu subway of th4th line in Shanghai[J].Chinese Journal of Rock Mechanics and Engineering,26(S1):2927~2934.
Ministry of Housing and Urban-Rural Construction of the People'Republic of China.2011.Code for Design of Building Foundation(GB50007-2011)[S].Beijing:China Architecture and Buildin Press.
Su T.2002.Technique and application study on dewatering of deep excavation in two-layer structure strata of soft soil zone[D]Wuhan:Wuhan University of Technology.
Wang C Y,Feng X L,Wang J W.2004.Hydrologic and geologi characteristics of medium and weak permeable layer in binar structural area in Hankou administrative region of Wuhan city[J]Yangtze River,35(9):27~29.
Wang J X,Feng B,Liu Y,et al.2012.Controlling subsidence caused b de-watering in a deep foundation pit[J].Bulletin of Engineerin Geology and the Environment,71(3):545~555.
Wang K D,Tong L Y,Wang Z S,et al.2014.Optimization of dewaterin wells in deep foundation pit considering effect of retainin structure[J].Chinese Journal of Geotechnical Engineering,36(S2):259~264.
Wang W.2002.The concept design method in foundation excavation engineering[J].Journal of Kunming University of Science and Technology,27(3):102~105.
Wu J C,Xue Y Q.2009.Groundwater dynamics[M].Beijing:Chin Water Power Press.
Wu L G,Li G,Fang Z C,et al.2009.Dewatering cases of foundation pit[M].Beijing:China Communications Press.
Ye X W,Ran L,Yi T H,et al.2012.Intelligent risk assessment fo dewatering of metro-tunnel deep excavations[J].Mathematica Problems in Engineering,(6):60~66.
Zhang L.2015.The study on the effect of anti-seepage curtain on supporting and drainage of deep foundation pit[D].Jinan:Shandong University.
Zhang X T.2013.Numerical analysis of the influence factors of supporting structure and soil deformation caused by foundation pi precipitation[D].Taiyuan:Taiyuan University of Technology.
崔永高.2015.深厚强透水含水层超大基坑降水群井效应研究[J]工程地质学报,23(3):574~579.
李小克,车向男,谭乐,等.2015.津湾广场9号楼超深软土基坑降水施工技术[J].施工技术,44(1):21~24,93.
李英,何忠泽,严桂华,等.2012.武汉二元结构地层基坑降水及其地面沉降研究[J].岩土工程学报,34(S1):767~772.
刘国彬,王洪新.2002.上海浅层粉砂地层承压水对基坑的危害及治理[J].岩土工程学报,24(6):790~792.
罗林峰,张林洪,杨松,等.2008.无黏性粗颗粒土的渗透性研究[J]云南水力发电,24(1):22~24.
骆祖江,李朗,曹惠宾,等.2006.复合含水层地区深基坑降水三维渗流场数值模拟---以上海环球金融中心基坑降水为例[J].工程地质学报,14(1):72~77.
骆祖江,张月萍,刘金宝.2007.复杂巨厚第四纪松散沉积层地区深基坑降水三维渗流场数值模拟---以上海地铁4#线董家渡段隧道修复基坑降水为例[J].岩石力学与工程学报,26(S1):2927~2934.
苏滔.2002.软土地区二元结构地层深基坑降低承压水技术和应用研究[D].武汉:武汉理工大学.
王翠英,冯晓腊,王继伟.2004.二元结构中弱透水层基坑降水的水文地质特性[J].人民长江,35(9):27~29.
王康达,童立元,王占生,等.2014.考虑围护结构影响的深基坑降压井布置方案优化[J].岩土工程学报,36(S2):259~264.
王伟.2002.基坑工程的概念设计[J].昆明理工大学学报,27(3):102~105.
吴吉春,薛禹群.2009.地下水动力学[M].北京:中国水利水电出版社.
吴林高,李国,方兆昌,等.2009.基坑工程降水案例[M].北京:人民交通出版社.
张柳.2015.止水帷幕在深基坑支护及降水中的作用效果研究[D]济南:山东大学.
张晓婷.2013.基坑降水对支护结构及土体变形影响因素的数值分析[D].太原:太原理工大学.
中华人民共和国住房和城乡建设部.2011.建筑地基基础设计规范(GB50007-2011)[S].北京:中国建筑工业出版社.
Li X K,Che X G,Tan L,et al.2015.Dewatering construction technolog of deep and soft foundation excavation in No.9 building of Jinwan Plaza[J].Construction Technology,44(1):21~24,93.
Li Y,He Z Z,Yan G H,et al.2012.Excavation dewatering and ground subsidence in dual structural stratum of Wuhan[J].Chinese Journa of Geotechnical Engineering,34(S1):767~772.
Liu G B,Wang H X.2002.Influence of the pressure water in shallow silt sand in Shanghai on excavation[J].Chinese Journal of Geotechnica Engineering,24(6):790~792.
Luo L F,Zhang L H,Yang S,et al.2008.Study on permeability o cohesionless coarse-grained soil[J].Yunnan Water Power,24(1):22~24.
Luo Z J,Li L,Cao H B,et al.2006.Numerical simulation of threedimensional seepage field of a deep foundation pit during dewaterin in a complex composite aquifer system---case study of dewaterin of a pit at the Shanghai Finance Center[J].Journal of Engineerin Geology,14(1):72~77.
Luo Z J,Zhang Y P,Liu J B.2007.Three-dimensional seepage numerica simulation of deep foundation pit dewatering in complicated quaternary loose sediments with great thickness-a case study o dewatering reconstructed foundation pit at Dongjiadu subway of th4th line in Shanghai[J].Chinese Journal of Rock Mechanics and Engineering,26(S1):2927~2934.
Ministry of Housing and Urban-Rural Construction of the People'Republic of China.2011.Code for Design of Building Foundation(GB50007-2011)[S].Beijing:China Architecture and Buildin Press.
Su T.2002.Technique and application study on dewatering of deep excavation in two-layer structure strata of soft soil zone[D]Wuhan:Wuhan University of Technology.
Wang C Y,Feng X L,Wang J W.2004.Hydrologic and geologi characteristics of medium and weak permeable layer in binar structural area in Hankou administrative region of Wuhan city[J]Yangtze River,35(9):27~29.
Wang J X,Feng B,Liu Y,et al.2012.Controlling subsidence caused b de-watering in a deep foundation pit[J].Bulletin of Engineerin Geology and the Environment,71(3):545~555.
Wang K D,Tong L Y,Wang Z S,et al.2014.Optimization of dewaterin wells in deep foundation pit considering effect of retainin structure[J].Chinese Journal of Geotechnical Engineering,36(S2):259~264.
Wang W.2002.The concept design method in foundation excavation engineering[J].Journal of Kunming University of Science and Technology,27(3):102~105.
Wu J C,Xue Y Q.2009.Groundwater dynamics[M].Beijing:Chin Water Power Press.
Wu L G,Li G,Fang Z C,et al.2009.Dewatering cases of foundation pit[M].Beijing:China Communications Press.
Ye X W,Ran L,Yi T H,et al.2012.Intelligent risk assessment fo dewatering of metro-tunnel deep excavations[J].Mathematica Problems in Engineering,(6):60~66.
Zhang L.2015.The study on the effect of anti-seepage curtain on supporting and drainage of deep foundation pit[D].Jinan:Shandong University.
Zhang X T.2013.Numerical analysis of the influence factors of supporting structure and soil deformation caused by foundation pi precipitation[D].Taiyuan:Taiyuan University of Technology.
崔永高.2015.深厚强透水含水层超大基坑降水群井效应研究[J]工程地质学报,23(3):574~579.
李小克,车向男,谭乐,等.2015.津湾广场9号楼超深软土基坑降水施工技术[J].施工技术,44(1):21~24,93.
李英,何忠泽,严桂华,等.2012.武汉二元结构地层基坑降水及其地面沉降研究[J].岩土工程学报,34(S1):767~772.
刘国彬,王洪新.2002.上海浅层粉砂地层承压水对基坑的危害及治理[J].岩土工程学报,24(6):790~792.
罗林峰,张林洪,杨松,等.2008.无黏性粗颗粒土的渗透性研究[J]云南水力发电,24(1):22~24.
骆祖江,李朗,曹惠宾,等.2006.复合含水层地区深基坑降水三维渗流场数值模拟---以上海环球金融中心基坑降水为例[J].工程地质学报,14(1):72~77.
骆祖江,张月萍,刘金宝.2007.复杂巨厚第四纪松散沉积层地区深基坑降水三维渗流场数值模拟---以上海地铁4#线董家渡段隧道修复基坑降水为例[J].岩石力学与工程学报,26(S1):2927~2934.
苏滔.2002.软土地区二元结构地层深基坑降低承压水技术和应用研究[D].武汉:武汉理工大学.
王翠英,冯晓腊,王继伟.2004.二元结构中弱透水层基坑降水的水文地质特性[J].人民长江,35(9):27~29.
王康达,童立元,王占生,等.2014.考虑围护结构影响的深基坑降压井布置方案优化[J].岩土工程学报,36(S2):259~264.
王伟.2002.基坑工程的概念设计[J].昆明理工大学学报,27(3):102~105.
吴吉春,薛禹群.2009.地下水动力学[M].北京:中国水利水电出版社.
吴林高,李国,方兆昌,等.2009.基坑工程降水案例[M].北京:人民交通出版社.
张柳.2015.止水帷幕在深基坑支护及降水中的作用效果研究[D]济南:山东大学.
张晓婷.2013.基坑降水对支护结构及土体变形影响因素的数值分析[D].太原:太原理工大学.
中华人民共和国住房和城乡建设部.2011.建筑地基基础设计规范(GB50007-2011)[S].北京:中国建筑工业出版社.