Responses of the Strata and Supporting System to Dewatering in Deep Excavations

doi:10.1007/s12204-017-1884-7

Abstract

Abstract: In order to prevent the inrushing caused by deep excavations, dewatering measure has to be adopted to decrease the confined water level. In this study, the responses of the strata and supporting system to dewatering in deep excavations are investigated through numerical simulations and case studies. Coupled fluid-mechanical analyses are performed by the use of the numerical software, FLAC3D. The responses of the ground settlement, base heave and interior columns to the excavation and dewatering are analyzed. Numerical results indicate that the dewatering measure can effectively reduce the uplift of the subsurface soil in the excavation, and decrease the vertical displacement of the supporting system. In addition, field data of two case histories show the similar responses and confirm the validation of the numerical results. Based on the analyses, dewatering in the confined aquifer is recommended as a construction method for controlling the vertical displacement of the strata and supporting system in deep excavations.

Key words: deep excavations| column| confined water| numerical simulation| dewatering measure

摘要： In order to prevent the inrushing caused by deep excavations, dewatering measure has to be adopted to decrease the confined water level. In this study, the responses of the strata and supporting system to dewatering in deep excavations are investigated through numerical simulations and case studies. Coupled fluid-mechanical analyses are performed by the use of the numerical software, FLAC3D. The responses of the ground settlement, base heave and interior columns to the excavation and dewatering are analyzed. Numerical results indicate that the dewatering measure can effectively reduce the uplift of the subsurface soil in the excavation, and decrease the vertical displacement of the supporting system. In addition, field data of two case histories show the similar responses and confirm the validation of the numerical results. Based on the analyses, dewatering in the confined aquifer is recommended as a construction method for controlling the vertical displacement of the strata and supporting system in deep excavations.

关键词: deep excavations| column| confined water| numerical simulation| dewatering measure

CLC Number:

TU 473.3

XIAO Xiao (肖潇), ZHANG Yangqing (张扬清), LI Mingguang* (李明广), WANG Jianhua (王建华). Responses of the Strata and Supporting System to Dewatering in Deep Excavations[J]. Journal of Shanghai Jiao Tong University (Science), 2017, 22(6): 705-711.

References 24

[1]	OU C Y, HSIEH P G, CHIOU D C. Characteristics ofground surface settlement during excavation [J]. Canadian Geotechnical Journal, 1993, 30(5): 758-767.
[2]	NG C W W. Observed performance of multiproppedexcavation in stiff clay [J]. Journal of Geotechnical andGeoenvironmental Engineering, 1998, 124(9): 889-905.
[3]	MOORMANN C. Analysis of wall and ground movementsdue to deep excavations in soft soil based ona new worldwide database [J]. Soils and Foundations,2004, 44(1): 87-98.
[4]	WANG Z W, NG C W, LIU G B. Characteristicsof wall deflections and ground surface settlements inShanghai [J]. Canadian Geotechnical Journal, 2005,42(42): 1243-1254.
[5]	O’ROURKE T D, MCGINN A J. Lessons learnedfor ground movements and soil stabilization from theBoston Central Artery [J]. Journal of Geotechnical andGeoenvironmental Engineering, 2006, 132(8): 966-989.
[6]	WANG J H, XU Z H, WANG W D. Wall and groundmovements due to deep excavations in Shanghai softsoils [J]. Journal of Geotechnical and GeoenvironmentalEngineering, 2010, 136(7): 985-994.
[7]	HUANG Y, BAO Y J, WANG Y H. Analysis of geoenvironmentalhazards in urban underground space developmentin Shanghai [J]. Natural Hazards, 2015,75(3): 2067-2079.
[8]	TAN Y, LI M W. Measured performance of a 26 mdeep top-down excavation in downtown Shanghai [J].Canadian Geotechnical Journal, 2011, 48(5): 704-719.
[9]	SHARMA J S, HEFNY A M, ZHAO J, et al. Effectof large excavation on deformation of adjacent MRTtunnels [J]. Tunnelling and Underground Space Technology,2001, 16(2): 93-98.
[10]	ZDRAVKOVIC L, POTTS D M, ST JOHN H D. Modellingof a 3D excavation in finite element analysis [J].G′eotechnique, 2005, 55(7): 497-513.
[11]	KUNG G T C, OU C Y, JUANG C H. Modeling smallstrainbehavior of Taipei clays for finite element analysisof braced excavations [J]. Computers and Geotechnics,2009, 36(1/2): 304-319.
[12]	HONG Y, NG CWW. Base stability of multi-proppedexcavations in soft clay subjected to hydraulic uplift[J]. Canadian Geotechnical Journal, 2013, 50(2): 153-164(12).
[13]	HUANG Y, YANG Y, LI J L. Numerical simulationof artificial groundwater recharge for controlling landsubsidence [J]. KSCE Journal of Civil Engineering,2015, 19(2): 418-426.
[14]	WU Y X, SHEN S L, YIN Z Y, et al. Characteristics ofgroundwater seepage with cut-off wall in gravel aquiferI: Field observations [J]. Canadian Geotechnical Journal,2015, 52(10): 108-116.
[15]	LIU J, CHEN J J, WANG J H. Fluid-structure couplinganalysis of dewatering and excavation in 500 kVShanghai Expo underground substation [J]. Journal ofShanghai Jiao Tong University, 2010, 44(6): 721-725(in Chinese)
[16]	TAN Y P, CHEN J J, WANG J H. Practical investigationinto two types of analyses in predicting ground displacementsdue to dewatering and excavation [J]. Journalof Aerospace Engineering, 2014, 28(6): A4014001.
[17]	Itasca Consulting Group Inc. FLAC3D V.5.0: FastLagrangian analysis of continua in 3 dimensions [Z].Minnesota: Itasca Consulting Group Inc, 2016.
[18]	DONG Y P, BURD H J, HOULSBY G T. Finiteelementanalysis of a deep excavation case history [J].G′eotechnique, 2015, 66(1): 1-15.
[19]	OU C Y, HSIEH P G, LIN Y L. A parametric studyof wall deflections in deep excavations with the installationof cross walls [J]. Computers and Geotechnics,2013, 50(5): 55-65.
[20]	Shanghai Municipal Commission of City Developmentand Transport. Foundation design code: DGJ08-11-2010 [S]. Shanghai: Shanghai Xian Dai ArchitecturalDesign (Group) Co., Ltd., 2010.
[21]	CHEN J J,WANG J H, XIANG GW, et al. Numericalstudy on the movement of existing tunnel due to deepexcavation in Shanghai [J]. Geotechnical EngineeringJournal of the SEAGS and AGSSEA, 2011, 42(3): 30-40.
[22]	SHI J W, LIU G B, HUANG P, et al. Interaction betweena large-scale triangular excavation and adjacentstructures in Shanghai soft clay [J]. Tunnelling andUnderground Space Technology, 2015, 50: 282-295.
[23]	WANG W, DOU J Z, CHEN J J, et al. Numerical analysisof the soil compaction degree under multi-locationtamping [J]. Journal of Shanghai Jiao Tong University(Science), 2017, 22(4): 417-433.
[24]	TAN Y, WANG D L. Characteristics of a large-scaledeep foundation pit excavated by the central-islandtechnique in Shanghai soft clay. I: Bottom-up constructionof the central cylindrical shaft [J]. Journalof Geotechnical and Geoenvironmental Engineering,2013, 139(11): 1875-1893.