复杂地层中基坑降水引发的水位及沉降分析与控制对策
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摘要
在深大基坑工程中,若止水帷幕设置不合理,基坑内外水力联系将不能被完全截断,这样基坑内降水不但会引起坑外土体沉降,还会引发围护结构变形。在天津地铁5号线某车站基坑工程中,由于场地地层较为复杂,含水层不连续且存在大量透镜体,因此在开挖前进行了预降水试验,判断基坑内外水力联系。文章通过对预降水试验进行数据分析得出,该基坑内外承压含水层连通,且各含水层存在水力联系,原设计的落底式止水帷幕未能彻底截断承压含水层,造成了较大的围护结构变形与显著的建筑物沉降。因此,当场地承压含水层构造较为复杂时,应当在勘察阶段进行场地抽水试验,或者在基坑开挖前进行预降水试验,以全面掌握场地水文地质情况及基坑内外含水层水力联系。同时预降水前应在坑外合理设置回灌井,避免降水引发坑外沉降,并提前施工基坑第一道水平支撑,增加围护结构抗侧移刚度,减小降水引发的围护结构变形。
If the arrangement of the curtain is unreasonable in deep foundation, the hydraulic connection of both side of the foundation will still exist, which lead to the ground settlement and the deformation of the diaphragm wall. In an engineering of Tianjin 5 th metro station, the condition is complicated and many lens are discovered in the discontinuous aquifer. Pre-dewatering test was carried out before the excavation to judge the foundation hydraulic connection. This paper made an observation about the pre-dewatering test. After analyzing, it can be included that there's hydraulic connection in both side of the diaphragm wall. The different confined aquifer has hydraulic connection, either. The confined aquifer can't be truncated by the curtain, which caused ground settlement and clear deformation of the diaphragm wall. Therefore, in the complicated condition, pre-dewatering test before the excavation and pumping during the geological survey should be carried out to judge the connection of the aquifer and the geological condition. To decrease the ground settlement, recharge well should be built before pumping. Building the first lateral support construction can improve the lateral stiffness and reduce the deformation of the diaphragm wall caused by dewatering effectively.
If the arrangement of the curtain is unreasonable in deep foundation, the hydraulic connection of both side of the foundation will still exist, which lead to the ground settlement and the deformation of the diaphragm wall. In an engineering of Tianjin 5 th metro station, the condition is complicated and many lens are discovered in the discontinuous aquifer. Pre-dewatering test was carried out before the excavation to judge the foundation hydraulic connection. This paper made an observation about the pre-dewatering test. After analyzing, it can be included that there's hydraulic connection in both side of the diaphragm wall. The different confined aquifer has hydraulic connection, either. The confined aquifer can't be truncated by the curtain, which caused ground settlement and clear deformation of the diaphragm wall. Therefore, in the complicated condition, pre-dewatering test before the excavation and pumping during the geological survey should be carried out to judge the connection of the aquifer and the geological condition. To decrease the ground settlement, recharge well should be built before pumping. Building the first lateral support construction can improve the lateral stiffness and reduce the deformation of the diaphragm wall caused by dewatering effectively.
引文
[1]田志强,陈锐,王子哲,等.深基坑开挖及降水引起的邻近浅基础沉降分析[J].地下空间与工程学报,2012,8(增1):1483-1490(Tian Zhiqiang,Chen Rui,Wang Zizhe,et al.Settlement of shallow foundation induced by adjacent deep excavation and dewatering[J].Chinese Journal of Underground Space and Engineering,2012,8(S1):1483-1490(in Chinese))
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[3]金小荣,俞建霖,祝哨晨,等.基坑降水引起周围土体沉降性状分析[J].岩土力学,2005,26(10):54-60(Jin Xiaorong,Yu Jianlin,Zhu Shaochen,et al.Analysis of behaviors of settlement of pit’s surrounding soils by dewatering[J].Rock and Soil Mechanics,2005,26(10):54-60(in Chinese))
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[5]肖铭钊,冯晓腊,陈新国,等.悬挂式止水帷幕对基坑降水影响的定量研究[J].市政技术,2009,27(增2):286-289,292(Xiao Mingzhao,Feng Xiaola,Chen xinguo,et al.Study on the influence of pensile curtain to dewatering[J].Municipal Engineering Technology,2009,27(S2):286-289,292(in Chinese))
[6]周火垚,王华钦,张维泉.悬挂式止水在基坑工程中的应用[J].岩土工程学报,2012,34(增1):470-473(Zhou Huoyao,Wang Huaqin,Zhuang Weiquan.Application of pensile impervious curtain to excavations[J].Chinese Journal of Geotechnical Engineering,2012,34(S1):470-473(in Chinese))
[7]郑刚,曹剑然,程雪松,等.天津第二粉土粉砂微承含水层回灌试验研究[J].岩土工程学报,2018,40(4):592-601(Zheng Gang,Cao Jianran,Cheng Xuesong,et al.Experimental study on artificial recharge of second Tianjin silt and silty sand micro-confined aquifer[J].Chinese Journal of Geotechnical Engineering,2018,40(4):592-601(in Chinese))
[8]卢智强,冯晓腊,王超峰.悬挂式止水帷幕对基坑降水的影响[J].隧道建设,2006(5):5-7,20(Lu Zhiqiang,Feng Xiaola,Wang Chaofeng.Effects of pensile curtains on dewatering of foundation pits[J].Tunnel Construction,2006(5):5-7,20(in Chinese))
[9]刘伟.深厚富水地层深基坑新型止水封底帷幕的设计与施工[J].矿业安全与环保,2018,45(5):83-86(Liu Wei.Designing and construction of new type of water stop bottom curtain for deep foundation pit in thick stratum with abundant water[J].Mining Safety&Environmental Protection,2018,45(5):83-86(in Chinese))
[10]张莲花,孔德坊.沉降变形控制的基坑降水最优化方法及应用[J].岩土工程学报,2005,27(10):1171-1174(Zhang Lianhua,Kong Defang.Optimum method of dewatering controlled by surrounding settlement and its application[J].Chinese Journal of Geotechnical Engineering,2005,27(10):1171-1174(in Chinese))
[11]Harris D I,Mair R J,Love J P,et al.Observations of ground and structure movements for compensation grouting during tunnel construction at Waterloo station[J].Geotechnique,1994,44(4):691-713
[12]张尚根,陈志龙,曹继勇.深基坑周围地表沉降分析[J].岩土工程技术,1999(4):7-9(Zhang Shanggen,Chen Zhilong,Cao Jiyong.Analyze of the settlement surrounding by the deep foundation[J].Geotechnical Engineering Technique,1999(4):7-9(in Chinese))
[13]王建秀,郭太平,吴林高,等.深基坑降水中墙-井作用机理及工程应用[J].地下空间与工程学报,2010,6(3):564-570(Wang Jianxiu,Guo Taiping,Wu Lingao,et al.Mechanism and application of interaction between underground wall and well in dewatering for deep excavation[J].Chinese Journal of Underground space and Engineering,2010,6(3):564-570(in Chinese))
[14]施成华,彭立敏.基坑开挖及降水引起的地表沉降预测[J].土木工程学报,2006,39(5):117-121(Shi Chenghua,Peng Limin.Ground surface settlement caused by foundation pit excavation and dewatering[J].China Civil Engineering Journal,2006,39(5):117-121(in Chinese))
[15]戴斌,王卫东.受承压水影响深基坑工程的若干技术措施探讨[J].岩土工程学报,2006,28(增1):1659-1663(Dai Bin,Wang Weidong.Discussions on technologies of deep foundation pit projects affected by confined water[J].Chinese Journal of Geotechnical Engineering,2006,28(S1):1659-1663(in Chinese))
[16]李琳.工程降水对深基坑性状及周围环境影响的研究[D].上海:同济大学,2007(Li Lin.Study on the effect of surrounding by deep foundation dewatering[D].Shanghai:Tongji University,2007(in Chinese))
[17]时伟,刘继明,章伟.深基坑桩锚支护体系水平位移试验研究[J].岩土力学与工程学报,2003,22(1):2355-2358(Shi Wei,Liu Jiming,Zhang Wei.Testing study on horizontal displacement of anchor-pile bracing structure for deep foundation pit[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(1):2355-2358(in Chinese))
[18]曾超峰,薛秀丽,郑刚.软土区基坑预降水引起支护墙侧移的典型参数影响研究[J].岩土力学,2017,38(11):3295-3303,3318(Zeng Chaofeng,Xue Xiuli,Zheng Gang.A parametric study of lateral displacement of support wall induced by foundation pre-dewatering in soft ground[J].Rock and Soil Machanics,2017,38(11):3295-3303,3318(in Chinese))
[19]蔡来炳,周红波.城市轨道交通深基坑工程承压水风险与控制研究[J].防灾减灾工程学报,2015,35(5):617-623(Cai Laibing,Zhou Hongbo.Risk of the artesian water and control measurements for the deep excavation of urban rail transit engineering[J].Journal of Disaster Prevention and Mitigation Engineering,2015,35(5):617-623(in Chinese))
[20]曾超峰.工程降水引起基坑及土体变形机理、规律及控制策略研究[D].天津:天津大学,2014(Zeng Chaofeng.Study on deformation mechanism,behavior and control strategy of excavation and ground under dewatering[D].Tianjin:Tianjin University,2014(in Chinese))
[2]Zhang Y Q,Wang J H,Chen J J,et al.Numerical study on the responses of groundwater and strata to pumping and recharge in a deep confined aquifer[J].Journal of Hydrology,2017,548:342-352
[3]金小荣,俞建霖,祝哨晨,等.基坑降水引起周围土体沉降性状分析[J].岩土力学,2005,26(10):54-60(Jin Xiaorong,Yu Jianlin,Zhu Shaochen,et al.Analysis of behaviors of settlement of pit’s surrounding soils by dewatering[J].Rock and Soil Mechanics,2005,26(10):54-60(in Chinese))
[4]冯晓腊,谢武军,卢智强,等.悬挂式止水帷幕对基坑降水的影响[J].土工基础,2006,20(4):33-36(Feng Xiaola,Xie Wujun,Lu Zhiqiang,et al.Effects of suspended impervious curtain on foundation dewatering[J].Soil Engineering and Foundation,2006,20(4):33-36(in Chinese))
[5]肖铭钊,冯晓腊,陈新国,等.悬挂式止水帷幕对基坑降水影响的定量研究[J].市政技术,2009,27(增2):286-289,292(Xiao Mingzhao,Feng Xiaola,Chen xinguo,et al.Study on the influence of pensile curtain to dewatering[J].Municipal Engineering Technology,2009,27(S2):286-289,292(in Chinese))
[6]周火垚,王华钦,张维泉.悬挂式止水在基坑工程中的应用[J].岩土工程学报,2012,34(增1):470-473(Zhou Huoyao,Wang Huaqin,Zhuang Weiquan.Application of pensile impervious curtain to excavations[J].Chinese Journal of Geotechnical Engineering,2012,34(S1):470-473(in Chinese))
[7]郑刚,曹剑然,程雪松,等.天津第二粉土粉砂微承含水层回灌试验研究[J].岩土工程学报,2018,40(4):592-601(Zheng Gang,Cao Jianran,Cheng Xuesong,et al.Experimental study on artificial recharge of second Tianjin silt and silty sand micro-confined aquifer[J].Chinese Journal of Geotechnical Engineering,2018,40(4):592-601(in Chinese))
[8]卢智强,冯晓腊,王超峰.悬挂式止水帷幕对基坑降水的影响[J].隧道建设,2006(5):5-7,20(Lu Zhiqiang,Feng Xiaola,Wang Chaofeng.Effects of pensile curtains on dewatering of foundation pits[J].Tunnel Construction,2006(5):5-7,20(in Chinese))
[9]刘伟.深厚富水地层深基坑新型止水封底帷幕的设计与施工[J].矿业安全与环保,2018,45(5):83-86(Liu Wei.Designing and construction of new type of water stop bottom curtain for deep foundation pit in thick stratum with abundant water[J].Mining Safety&Environmental Protection,2018,45(5):83-86(in Chinese))
[10]张莲花,孔德坊.沉降变形控制的基坑降水最优化方法及应用[J].岩土工程学报,2005,27(10):1171-1174(Zhang Lianhua,Kong Defang.Optimum method of dewatering controlled by surrounding settlement and its application[J].Chinese Journal of Geotechnical Engineering,2005,27(10):1171-1174(in Chinese))
[11]Harris D I,Mair R J,Love J P,et al.Observations of ground and structure movements for compensation grouting during tunnel construction at Waterloo station[J].Geotechnique,1994,44(4):691-713
[12]张尚根,陈志龙,曹继勇.深基坑周围地表沉降分析[J].岩土工程技术,1999(4):7-9(Zhang Shanggen,Chen Zhilong,Cao Jiyong.Analyze of the settlement surrounding by the deep foundation[J].Geotechnical Engineering Technique,1999(4):7-9(in Chinese))
[13]王建秀,郭太平,吴林高,等.深基坑降水中墙-井作用机理及工程应用[J].地下空间与工程学报,2010,6(3):564-570(Wang Jianxiu,Guo Taiping,Wu Lingao,et al.Mechanism and application of interaction between underground wall and well in dewatering for deep excavation[J].Chinese Journal of Underground space and Engineering,2010,6(3):564-570(in Chinese))
[14]施成华,彭立敏.基坑开挖及降水引起的地表沉降预测[J].土木工程学报,2006,39(5):117-121(Shi Chenghua,Peng Limin.Ground surface settlement caused by foundation pit excavation and dewatering[J].China Civil Engineering Journal,2006,39(5):117-121(in Chinese))
[15]戴斌,王卫东.受承压水影响深基坑工程的若干技术措施探讨[J].岩土工程学报,2006,28(增1):1659-1663(Dai Bin,Wang Weidong.Discussions on technologies of deep foundation pit projects affected by confined water[J].Chinese Journal of Geotechnical Engineering,2006,28(S1):1659-1663(in Chinese))
[16]李琳.工程降水对深基坑性状及周围环境影响的研究[D].上海:同济大学,2007(Li Lin.Study on the effect of surrounding by deep foundation dewatering[D].Shanghai:Tongji University,2007(in Chinese))
[17]时伟,刘继明,章伟.深基坑桩锚支护体系水平位移试验研究[J].岩土力学与工程学报,2003,22(1):2355-2358(Shi Wei,Liu Jiming,Zhang Wei.Testing study on horizontal displacement of anchor-pile bracing structure for deep foundation pit[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(1):2355-2358(in Chinese))
[18]曾超峰,薛秀丽,郑刚.软土区基坑预降水引起支护墙侧移的典型参数影响研究[J].岩土力学,2017,38(11):3295-3303,3318(Zeng Chaofeng,Xue Xiuli,Zheng Gang.A parametric study of lateral displacement of support wall induced by foundation pre-dewatering in soft ground[J].Rock and Soil Machanics,2017,38(11):3295-3303,3318(in Chinese))
[19]蔡来炳,周红波.城市轨道交通深基坑工程承压水风险与控制研究[J].防灾减灾工程学报,2015,35(5):617-623(Cai Laibing,Zhou Hongbo.Risk of the artesian water and control measurements for the deep excavation of urban rail transit engineering[J].Journal of Disaster Prevention and Mitigation Engineering,2015,35(5):617-623(in Chinese))
[20]曾超峰.工程降水引起基坑及土体变形机理、规律及控制策略研究[D].天津:天津大学,2014(Zeng Chaofeng.Study on deformation mechanism,behavior and control strategy of excavation and ground under dewatering[D].Tianjin:Tianjin University,2014(in Chinese))