地下水渗流对悬挂式止水帷幕基坑变形影响
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摘要
以某透水性土层较深的悬挂式止水帷幕基坑为背景,采用ABAQUS建立考虑分级降水开挖全过程的三维流固耦合模型,研究降水对于基坑变形发展的影响规律和不利因素,分析开挖前预降水深度、止水帷幕深度对基坑变形性状的影响.研究表明:渗流与开挖支护具有明显的耦合效应,降水引起的围护结构侧移增量模式随开挖和支撑施作情况不同而差异较大,降水引起的地表沉降是由土体固结和渗流引起的围护结构侧移引发的地表沉降组成;地表沉降影响范围较经验预测值明显偏大,在基坑西侧地表沉降最大点,降水施工期累积产生的沉降约占48%;各级降水中第1级降水对基坑变形最不利,围护结构初始侧移随第1级降水深度的增加而快速增长,使得竣工后的最大围护结构侧移和坑外地表沉降呈指数增长;止水帷幕对于减少坑外水位下降和控制地表沉降有显著作用,随着帷幕深度的增加,地表最大沉降和沉降影响范围降低,存在最优止水帷幕深度使得帷幕超过最优深度后地表沉降趋于稳定.
Taking the deep foundation pit with a suspended impervious curtain as an example, ABAQUS was used to establish the three-dimensional fluid-solid coupling model considering the whole process of grading precipitation and excavation in order to analyze the influence and unfavorable factors of precipitation on the deformation of the foundation pit. Then the depth of first-stage precipitation and the impervious curtain were analyzed. Results show that seepage and excavation support have coupling effects. The lateral displacement increment of support piles caused by precipitation varies with the conditions of excavation support. The ground settlement caused by precipitation is influenced by soil consolidation and the lateral displacement of support piles caused by precipitation.The scope of ground settlement is larger than that of empirical prediction, and precipitation-induced settlement accounts for 48% at the maximum point of settlement. The first-stage precipitation is the most unfavorable to the foundation pit of all stages of precipitation. The initial lateral displacement of support piles increases rapidly with the increase of the first-stage precipitation depth, so that the growth of the final maximum lateral displacement of support piles and ground settlement is exponential. The impervious curtain can effectively reduce the water level outside the foundation pit drop and control ground settlement. The maximum ground settlement and the scope of ground settlement decrease as the depth of the impervious curtain increases. There is an optimal curtain depth which makes ground settlement stabilize after the curtain depth exceeds the optimal depth.
Taking the deep foundation pit with a suspended impervious curtain as an example, ABAQUS was used to establish the three-dimensional fluid-solid coupling model considering the whole process of grading precipitation and excavation in order to analyze the influence and unfavorable factors of precipitation on the deformation of the foundation pit. Then the depth of first-stage precipitation and the impervious curtain were analyzed. Results show that seepage and excavation support have coupling effects. The lateral displacement increment of support piles caused by precipitation varies with the conditions of excavation support. The ground settlement caused by precipitation is influenced by soil consolidation and the lateral displacement of support piles caused by precipitation.The scope of ground settlement is larger than that of empirical prediction, and precipitation-induced settlement accounts for 48% at the maximum point of settlement. The first-stage precipitation is the most unfavorable to the foundation pit of all stages of precipitation. The initial lateral displacement of support piles increases rapidly with the increase of the first-stage precipitation depth, so that the growth of the final maximum lateral displacement of support piles and ground settlement is exponential. The impervious curtain can effectively reduce the water level outside the foundation pit drop and control ground settlement. The maximum ground settlement and the scope of ground settlement decrease as the depth of the impervious curtain increases. There is an optimal curtain depth which makes ground settlement stabilize after the curtain depth exceeds the optimal depth.
引文
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[13]张惠忠,刘明建.上海软土中的“微承压水”与基坑工程[J].岩土工程学报,2005,27(8):944-947.ZHANG Hui-zhong,LIU Ming-jian.‘Feeble confined water’in Shanghai area and related geotechnical engineering problems in foundation excavation[J].Chinese Jounal of Geotechnical Engineering,2005,27(8):944-947.
[14]关云飞,高峰,赵维炳,等.ANSYS软件中修正剑桥模型的二次开发[J].岩土力学,2010,31(3):976-980.GUAN Yun-fei,GAO Feng,ZHAO Wei-bing,et al.Secondary development of modified cambridge model in ANSYS software[J].Rock and Soil Mechanics,2010,31(3):976-980.
[15]CASⅡMAN P M,PREENS M.Groundwater lowering in construction:a practical guide to dewatering[M].2nd ed.Boca Raton:CRC Press,2012.
[16]王晓伟,童华炜.考虑深基坑坑角效应的支护结构变形计算[J].地下空间与工程学报,2011,7(3):479-484.WANG Xiao-wei,TONG Hua-wei.Deformation calculation of supporting structure considering deep excavation pit corner[J].Chinese Journal of Underground Space and Engineering,2011,7(3):479-484.
[17]刘国彬,王卫东.基坑工程手册[M].2版.北京:中国建筑工业出版社,2009:226.
[18]OU C Y,SHIAU B Y.Analysis of the corner effect on excavation behaviors[J].Canadian Geotechnical Journal,1998,35(3):532-540.
[19]刘丰敏.考虑初始水力坡度和层间补给的降水引起地面沉降研究[D].北京:中国建筑科学研究院,2016:117.
[20]曾超峰,薛秀丽,郑刚.软土地基渗透性条件对基坑降水过程中支护墙侧移的影响研究[J].岩土力学,2017,38(10):1-9.ZENG Chao-feng,XUE Xiu-li,ZHENG Gang.Effect of soil permeability on wall deflection during preexcavation dewatering in soft ground[J].Rock and Soil Mechanics,2017,38(10):1-9.
[21]徐中华.上海地区支护结构与主体地下结构相结合的深基坑变形性状研究[D].上海:上海交通大学,2007:35.
[22]HSIEH P G,OU C Y.Shape of ground surface settlement profiles caused by excavation[J].Canadian Geotechnical Journal,1998,35(6):1004-1017.
[23]李方明,陈国兴.江漫滩悬挂式止水帷幕基坑地表沉降变形研究[J].隧道建设,2018,38(1):33-40.LI Fang-ming,CHEN Guo-xing.Study of ground settlement of foundation pit with suspended waterproof curtain in Yangtze River floodplain[J].Tunnel Construction,2018,38(1):33-40.
[24]吴意谦,朱彦鹏.潜水地区基坑降水诱发地面沉降的一种改进算法[J].浙江大学学报:工学版,2016,50(11):2188-2197.WU Yi-qian,ZHU Yan-peng.Improved calculation of settlement due to dewatering of foundation pits in phreatic aquifer[J].Journal of Zhejiang University:Engineering Science,2016,50(11):2188-2197.
[25]康志军,谭勇,李想,等.基坑围护结构最大侧移深度对周边环境的影响[J].岩土力学,2016,37(10):2909-2914.KANG Zhi-jun,TAN Yong,LI Xiang,et al.Influences of depth of maximum lateral deflection of excavation support on adjacent environment[J].Rock and Soil Mechanics,2016,37(10):2909-2914.
[2]LIU G B,NG C W W,WANG Z W.Observed performance of a deep multistrutted excavation in Shanghai soft clays[J].Journal of Geotechnical and Geoenvironmental Engineering,2005,131(8):1004-1013.
[3]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 Cheng-hua,PENG Li-min.Ground surface settlement caused by foundation pit excavation and dewatering[J].China Civil Engineering Journal,2006,39(5):117-121.
[4]冯怀平,张伏光,岳祖润.考虑流固耦合作用的深基坑有限元分析[J].地下空间与工程学报,2012,8(2):286-291.FENG Huai-ping,ZHANG Fu-guang,YUE Zu-run.Numerical analysis of excavation considering the coupling of seepage field and stress field[J].Chinese Journal of Underground Space and Engineering,2012,8(2):286-291.
[5]张小伟,姚笑青.基坑工程变形的渗流应力耦合有限元分析[J].地下空间与工程学报,2012,08(2):339-344.ZHANG Xiao-wei,YAO Xiao-qing.The seepagestress coupled finite element analysis of foundation pit deformation[J].Chinese Journal of Underground Space and Engineering,2012,08(2):339-344.
[6]郑刚,曾超峰.基坑开挖前潜水降水引起的地下连续墙侧移研究[J].岩土工程学报,2013,35(12):2153-2163.ZHENG Gang,ZENG Chao-feng.Lateral displacement of diaphragm wall by dewatering of phreatic water before excavation[J].Chinese Journal of Geotechnical Engineering,2013,35(12):2153-2163.
[7]马少坤,邵羽,黄艳珍.基于孔隙比和渗透系数与深度相关的深基坑开挖变形分析[J].岩土工程学报,2013,35(Suppl.2):940-944.MA Shao-kun,SHAO Yu,HUANG Yan-zhen.Deformation of deep foundation pits due to excavation considering change of void ratio and permeability coefficient with depth[J].Chinese Journal of Geotechnical Engineering,2013,35(Suppl.2):940-944.
[8]曹力桥.软土地区深基坑开挖坑底隆起的有限元分析[J].岩土工程学报,2013,35(增2):819-824.CAO Li-qiao.Finite element method analysis of bottom upheaval of deep foundation pits in soft-clay ground due to excavation[J].Chinese Journal of Geotechnical Engineering,2013,35(Suppl.2):819-824.
[9]BIOT M A.Theory of elasticity and consolidation for a porous anisotropic solid[J].Journal of Applied Physics,1954,26(2):182-191.
[10]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(增刊):470-473.ZHOU Huo-yao,WANG Hua-qin,ZHANG Wei-quan.Application of pensile impervious curtain to excavations[J].Chinese Journal of Geotechnical Engineering,2012,34(Suppl.):470-473.
[11]曹净,汪尺,张丙军,等.成层土条件下坑底无可靠隔水层基坑渗流量分析[J].水动力学研究与进展,2016,31(1):83-89.CAO Jing,WANG Chi,ZHANG Bing-jun,et al.Seepage discharge analysis of soil layers of soil layers pit on no reliable impermeable layer[J].Chinese Journal of Hydrodynamics,2016,31(1):83-89.
[12]高旭,郭建波,晏鄂川.考虑止水帷幕的深基坑降水预测解析计算[J].岩土力学,2018,39(4):1-9.GAO Xu,GUO Jian-bo,YAN E-chuan.Dewatering forecast of deep foundation pit considering waterproof curtain using analytic approach[J].Rock and Soil Mechanics,2018,39(4):1-9.
[13]张惠忠,刘明建.上海软土中的“微承压水”与基坑工程[J].岩土工程学报,2005,27(8):944-947.ZHANG Hui-zhong,LIU Ming-jian.‘Feeble confined water’in Shanghai area and related geotechnical engineering problems in foundation excavation[J].Chinese Jounal of Geotechnical Engineering,2005,27(8):944-947.
[14]关云飞,高峰,赵维炳,等.ANSYS软件中修正剑桥模型的二次开发[J].岩土力学,2010,31(3):976-980.GUAN Yun-fei,GAO Feng,ZHAO Wei-bing,et al.Secondary development of modified cambridge model in ANSYS software[J].Rock and Soil Mechanics,2010,31(3):976-980.
[15]CASⅡMAN P M,PREENS M.Groundwater lowering in construction:a practical guide to dewatering[M].2nd ed.Boca Raton:CRC Press,2012.
[16]王晓伟,童华炜.考虑深基坑坑角效应的支护结构变形计算[J].地下空间与工程学报,2011,7(3):479-484.WANG Xiao-wei,TONG Hua-wei.Deformation calculation of supporting structure considering deep excavation pit corner[J].Chinese Journal of Underground Space and Engineering,2011,7(3):479-484.
[17]刘国彬,王卫东.基坑工程手册[M].2版.北京:中国建筑工业出版社,2009:226.
[18]OU C Y,SHIAU B Y.Analysis of the corner effect on excavation behaviors[J].Canadian Geotechnical Journal,1998,35(3):532-540.
[19]刘丰敏.考虑初始水力坡度和层间补给的降水引起地面沉降研究[D].北京:中国建筑科学研究院,2016:117.
[20]曾超峰,薛秀丽,郑刚.软土地基渗透性条件对基坑降水过程中支护墙侧移的影响研究[J].岩土力学,2017,38(10):1-9.ZENG Chao-feng,XUE Xiu-li,ZHENG Gang.Effect of soil permeability on wall deflection during preexcavation dewatering in soft ground[J].Rock and Soil Mechanics,2017,38(10):1-9.
[21]徐中华.上海地区支护结构与主体地下结构相结合的深基坑变形性状研究[D].上海:上海交通大学,2007:35.
[22]HSIEH P G,OU C Y.Shape of ground surface settlement profiles caused by excavation[J].Canadian Geotechnical Journal,1998,35(6):1004-1017.
[23]李方明,陈国兴.江漫滩悬挂式止水帷幕基坑地表沉降变形研究[J].隧道建设,2018,38(1):33-40.LI Fang-ming,CHEN Guo-xing.Study of ground settlement of foundation pit with suspended waterproof curtain in Yangtze River floodplain[J].Tunnel Construction,2018,38(1):33-40.
[24]吴意谦,朱彦鹏.潜水地区基坑降水诱发地面沉降的一种改进算法[J].浙江大学学报:工学版,2016,50(11):2188-2197.WU Yi-qian,ZHU Yan-peng.Improved calculation of settlement due to dewatering of foundation pits in phreatic aquifer[J].Journal of Zhejiang University:Engineering Science,2016,50(11):2188-2197.
[25]康志军,谭勇,李想,等.基坑围护结构最大侧移深度对周边环境的影响[J].岩土力学,2016,37(10):2909-2914.KANG Zhi-jun,TAN Yong,LI Xiang,et al.Influences of depth of maximum lateral deflection of excavation support on adjacent environment[J].Rock and Soil Mechanics,2016,37(10):2909-2914.