A numerical method considering the fluid-mechanical interaction is used to study the wall deformation and the ground settlements caused by dewatering in a confined aquifer in deep excavation. In the simulation of project example, the fluid-mechanical interaction methods based on the Biot’s consolidation theory are used to calculate the variation of settlements in deep excavation. Mechanics and seepage are iterated alternately to solve the deformation under combined effect of unloading and dewatering. The rationality of this method is verified by comparing with observed data. The three-dimensional numerical models of deep excavation are established. And the situations with or without dewatering are made direct comparison in terms of dewatering-induced wall deformations and ground surface settlements. By stripping the correlation curve of dewatering-induced additional settlements outside the pit, this paper focus on its discrepancies and mechanism with the comparison of one-dimensional consolidation theory based on the same pore pressure change. The results show that dewatering in the confined aquifer has less effects on wall deformation, but intensifies the magnitude and the influence range of total ground surface settlements. The dewatering-induced additional ground surface settlements outside 1.5 times of excavation depth of the pit match well with the settlements of one-dimensional consolidation theory, while the settlements discrepancy within 1.5 times of excavation depth behind the wall is mainly attributed to the soil-wall interaction.
ZHENG Qiyu,XIA Xiaohe,LI Mingguang,ZHANG Yangqing
. Influence of Dewatering in Confined Aquifers on Wall Deformation and
Ground Settlements in Deep Excavation[J]. Journal of Shanghai Jiaotong University, 2020
, 54(10)
: 1094
-1100
.
DOI: 10.16183/j.cnki.jsjtu.2019.157
［1］ZHANG Y Q, WANG J H, LI M G. Effect of dewatering in a confined aquifer on ground settlement in deep excavations［J］. International Journal of Geomechanics, 2018, 18(10): 04018120.
［2］LI M G, WANG J H, CHEN J J, et al. Responses of a newly built metro line connected to deep excavations in soft clay［J］. Journal of Performance of Constructed Facilities, 2017, 31(6): 04017096.
［3］ZENG C F, ZHENG G, XUE X L, et al. Combined recharge: A method to prevent ground settlement induced by redevelopment of recharge wells［J］. Journal of Hydrology, 2019, 568: 1-11.
［4］ZENG C F, XUE X L, ZHENG G, et al. Responses of retaining wall and surrounding ground to pre-excavation dewatering in an alternated multi-aquifer-aquitard system［J］. Journal of Hydrology, 2018, 559: 609-626.
［5］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.
［6］郑刚, 曾超峰, 薛秀丽. 承压含水层局部降压引起土体沉降机理及参数分析［J］. 岩土工程学报, 2014, 36(5): 802-817.
ZHENG Gang, ZENG Chaofeng, XUE Xiuli. Settlement mechanism of soils induced by local pressure-relief of confined aquifer and parameter analysis［J］. Chinese Journal of Geotechnical Engineering, 2014, 36(5): 802-817.
［7］ZHU Y F, HUANG Y, TAN Y P, et al. Stratified settlement characteristics of the soil strata in Shanghai due to dewatering［J］. Journal of Aerospace Engineering, 2014, 28(6): A4014005.
［8］WANG J X, DENG Y S, MA R Q, et al. Model test on partial expansion in stratified subsidence during foundation pit dewatering［J］. Journal of Hydrology, 2018, 557: 489-508.
［9］叶为民, 万敏, 陈宝, 等. 深基坑承压含水层降水对地面沉降的影响［J］. 地下空间与工程学报, 2009, 5(Sup.2): 1799-1805.
YE Weimin, WAN Min, CHEN Bao, et al. Influence of dewatering of confined aquifers on land subsidence during deep excavation［J］. Chinese Journal of Underground Space and Engineering, 2009, 5(Sup.2): 1799-1805.
［10］WANG J X, WU Y B, LIU X T, et al. Areal subsidence under pumping well-curtain interaction in subway foundation pit dewatering: Conceptual model and numerical simulations［J］. Environmental Earth Sciences, 2016, 75(3): 198.
［11］陈育民, 徐鼎平. FLAC/FLAC3D 基础与工程实例［M］.北京: 中国水利水电出版社, 2009.
CHEN Yumin, XU Dingping. FLAC/FLAC3D fundamentals and engineering applications［M］. Beijing: China Water & Power Press, 2009.
［12］LIM A, OU C Y. Stress paths in deep excavations under undrained conditions and its influence on deformation analysis［J］. Tunnelling and Underground Space Technology, 2017, 63: 118-132.
［13］HSIEH P G, OU C Y, LIN Y L. Three-dimensional numerical analysis of deep excavations with cross walls［J］. Acta Geotechnical, 2013, 8(1): 33-48.
［14］LIM A, OU C Y, HSIEH P G, Evaluation of clay constitutive models for analysis of deep excavation under undrained conditions［J］. Journal of GeoEngineering, 2010, 5(1): 9-20.
［15］DONG Y P, BURD H J, HOULSBY G T. Finite-element analysis of a deep excavation case history［J］. Géotechnique, 2016, 66(1): 1-15.
［16］上海市住房和城乡建设管理委员会. 基坑工程技术标准: DG/TJ 08-61-2018［S］. 上海: 同济大学出版社, 2018.
Shanghai Municipal Commission of Housing and Urban-Rural Development. Technical code for excavation engineering: DG/TJ 08-61-2018［S］. Shanghai: Tongji University Press, 2018.
［17］BEAR J, CORAPCIOGLU M Y. Mathematical model for regional land subsidence due to pumping: 1. Integrated aquifer subsidence equations based on vertical displacement only ［J］. Water Resources Research, 1981, 17(4): 937-946.
