In practice, dewatering for pressure relief is commonly undertaken during ongoing excavation to secure
bottom stability against basal upheaval. Simultaneously, through unloading, wall deflection is obviously observed.
Noticing that both cause soil deformations, this research is to study the effect of wall deformation on dewateringinduced
settlement. A coupled numerical analysis of finite-difference software is employed to model Shanghai
soft soils under multi-aquifer-aquitard systems (MAASs) by analyzing the results in association with an empirical
approach. Consequently, through gradual force reduction, shear strength at soil-wall interface is significantly
diminished. As wall deformation increases instantaneously upon lower loading, wall surface becomes deformedly
bending; this condition causes the challenge to workability of shear strength. Moreover, wall deformation caused
by unloading affects dewatering-induced settlement substantially. Under smaller loading, large wall deflection
is observed; soil plane of failure caused by both sliding and compression occurs along slip curve, with weaker
shear-strength soils at rD = 0.4 and stronger shear-strength soils between rD = 0.4 and rD = 0.65, where rD is the
distance from the wall that is normalized by the depth measured from ground surface. During dewatering, stronger
soils tend to drag weaker soils upward to reduce large differential settlements caused by additional compression.
Consequently, settlement becomes larger at rD = 0.4 and smaller at rD = 0.65. Remarkably, at rD > 2.3,
both settlement curves that result from numerical analysis and empirical method show overlapping; this indicates
that the unloading effect on dewatering-induced settlement at rD > 2.3 is insignificant. Furthermore, as wall
reaches maximum allowable wall deflection by 67% applied force, additional compression caused by dewatering
after loading remains smaller than that under 70% applied force, contributing to smaller dewatering-induced
settlement.
NAI Kimsrorng, LI Mingguang, CHEN Jinjian
. Effect of Wall Deformation on Dewatering-Induced Ground Surface Settlement[J]. Journal of Shanghai Jiaotong University(Science), 2020
, 25(4)
: 417
-425
.
DOI: 10.1007/s12204-020-2207-y
[1] MOORMANN C. Analysis of wall and ground movements due to deep excavations in soft soil based on a new worldwide database [J]. Soils and Foundations,2004, 44(1): 87-98.
[2] WANG Z W, NG C W W, LIU G B . Characteristics of wall deflections and ground surface settlements in Shanghai [J]. Canadian Geotechnical Journal, 2005,42(5): 1243-1254.
[3] WANG J H, XU Z H, WANG W D. Wall and ground movements due to deep excavations in Shanghai soft soils [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2010, 136(7): 985-994.
[4] 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.
[5] ZHOU N Q, VERMEER P A, LOU R X, et al. Numerical simulation of deep foundation pit dewatering and optimization of controlling land subsidence [J]. Engineering Geology, 2010, 114: 251-260.
[6] LUO Z J, ZHANG Y Y, WU Y X. Finite element numerical simulation of three-dimensional seepage control for deep foundation pit dewatering [J]. Journal of Hydrodynamics, 2008, 20(5): 596-602.
[7] 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.
[8] HELM D C. One-dimensional simulation of aquifer system compaction near Pixley, California: 2. Stressdependent parameters [J]. Water Resources Research,1976, 12(3): 375-391.
[9] GAMBOLATI G, FREEZE R A. Mathematical simulation of the subsidence of venice 1: Theory [J]. Water Resources Research, 1973, 9(3): 721-733.
[10] ZENG C F, XUE X L, ZHENG G, et al. Responses of retaining wall and surrounding ground to preexcavation dewatering in an alternated multi-aquiferaquitard system [J]. Journal of Hydrology, 2018, 559:609-626.
[11] ZHENG G, ZENG C F, DIAO Y, et al. Test and numerical research on wall deflections induced by preexcavation dewatering [J]. Computers and Geotechnics,2014, 62: 244-256.
[12] ZHENG G, DAI X, DIAO Y, et al. Experimental and simplified model study of the development of ground settlement under hazards induced by loss of groundwater and sand [J]. Natural Hazards, 2016, 82(3): 1869-1893.
[13] WANGJ 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.
[14] WU Y X, SHEN S L, WU H N, et al. Environmental protection using dewatering technology in a deep confined aquifer beneath a shallow aquifer [J]. Engineering Geology, 2015, 196: 59-70.
[15] TAN Y P, CHEN J J, WANG J H. Practical investigation into two types of analyses in predicting ground displacements due to dewatering and excavation [J]. Journal of Aerospace Engineering, 2015, 28(6): A4014001.
[16] 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.
[17] 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.
[18] XU Y S, SHEN S L, DU Y J. Geological and hydrogeological environment in Shanghai with geohazards to construction and maintenance of infrastructures [J].Engineering Geology, 2009, 109: 241-254.
[19] 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.
[20] DONG Y P, BURD H J, HOULSBY G T. Finiteelement analysis of a deep excavation case history [J].G′eotechnique, 2016, 66(1): 1-15.
[21] CHU S C. Rankine’s analysis of active and passive pressures in dry sands [J]. Japanese Society of Soils Mechanics and Foundations Engineering, 1991, 31(4):115-120.
