Analysis of Non-Darcy Flow in Aquitard at Bottom of Foundation Pit Under Fluctuation of Confined Water

doi:10.16183/j.cnki.jsjtu.2019.036

Abstract

Abstract:

In order to better explain the phenomenon of foundation pit inrush caused by confined water, the Hansbo non-Darcy seepage theory was introduced into the Terzaghi one-dimensional saturated soil consolidation equation. Finite difference methods were applied to the numerical solution of excess pore pressure caused by the fluctuation of confined water. Then, the numerical solution was reduced to Darcy seepage and compared with the analytical solution. The effects of non-Darcy parameters, fluctuation periods of confined water, and initial water levels on the variation of excess pore pressure in the aquitard were analyzed. The results show that the excess pore pressure in aquitard volatility increases over time under the fluctuation of confined water, and reaches a stable fluctuating state after several cycles. The greater the initial hydraulic gradient and test constant of non-Darcy, the more obvious the hysteresis phenomenon of excess pore pressure, and the smaller the amplitude. The longer period of pressure water fluctuation or the higher the initial water level, the greater the amplitude of excess pore pressure oscillation. In addition, when the base is subjected to higher levels of initial confined water, the excess pore pressure in aquitard becomes more susceptible to the change of confined water pressure. The application of a case indicates that the designed drawdown depth of the confined water level could be reduced if the non-Darcy factor is considered.

Key words: non-Darcy flow, foundation pit, excess pore pressure response, aquitard, exit gradient

CLC Number:

TU432

YING Hongwei, XU Dingye, WANG Di, ZHANG Lisha. Analysis of Non-Darcy Flow in Aquitard at Bottom of Foundation Pit Under Fluctuation of Confined Water[J]. Journal of Shanghai Jiao Tong University, 2020, 54(12): 1300-1306.

Figures/Tables 8

Fig.1

Fig.2

Fig.3

Fig.4

Fig.5

Fig.6

Fig.7

Fig.8

References 18

[1]	MILLIGAN V, LO K Y. Observations on some basal failures in sheeted excavations[J]. Canadian Geotechnical Journal, 1970, 7(2): 136-144.
[2]	车灿辉，张智博，刘实. 南京长江漫滩地区某深基坑突水原因分析及治理[J]. 岩土工程技术，2014, 28(4): 183-187.
	CHE Canhui, ZHANG Zhibo, LIU Shi. Analysis and management of confined water inrush of a deep foundation pit the floodplain area of Nanjing Yangtze River[J]. Geotechnical Engineering Technique, 2014, 28(4): 183-187.
[3]	徐长节，徐礼阁，孙凤明，等. 深基坑承压水的风险控制及处理实例[J]. 岩土力学，2014, 35(Sup.1): 353-358.
	XU Changjie, XU Lige, SUN Fengming, et al. Risk control and dealing example of confined water of deep foundation pit[J]. Rock and Soil Mechanics, 2014, 35(Sup.1): 353-358.
[4]	ZHOU P P, LI G M, LU Y D.Numerical modeling of tidal effects on groundwater dynamics in a multi-layered estuary aquifer system using equivalent tidal loading boundary condition: Case study in Zhanjiang, China[J]. Environmental Earth Sciences, 2016, 75(2): 1-16.
[5]	付丛生，陈建耀，曾松青，等. 滨海地区潮汐对地下水位变化影响的统计学分析[J]. 水利学报，2008, 39(12): 1365-1376.
	FU Congsheng, CHEN Jianyao, ZENG Songqing, et al. Statistical analysis on impact of tide on water table fluctuation in coastal aquifer[J]. Journal of Hydraulic Engineering, 2008, 39(12): 1365-1376.
[6]	HONG Y, NG C W W, WANGL Z. Initiation and failure mechanism of base instability of excavations in clay triggered by hydraulic uplift[J]. Canadian Geotechnical Journal, 2015, 52(5): 1-10.
[7]	丁春林. 软土地区承压水基坑突涌稳定计算法研究综述[J]. 地下空间与工程学报，2007, 3(2): 333-338.
	DING Chunlin. Summary of study on calculation method of inrushing for confined water foundation pit in soft soil area[J]. Chinese Journal of Underground Space and Engineering, 2007, 3(2): 333-338.
[8]	王玉林，谢康和，卢萌盟，等. 受承压水作用的基坑底板临界厚度的确定方法[J]. 岩土力学，2010, 31(5): 1539-1544.
	WANG Yulin, XIE Kanghe, LU Mengmeng, et al. A method for determining critical thickness of base soil of foundation pit subjected to confined water[J]. Rock and Soil Mechanics, 2010, 31(5): 1539-1544.
[9]	章丽莎，应宏伟，谢康和，等. 动态承压水作用下深基坑底部弱透水层的出逸比降解析研究[J]. 岩土工程学报，2017, 39(2): 295-300.
	ZHANG Lisha, YING Hongwei, XIE Kanghe, et al. Analytical study on exit gradient at base aquitard of deep excavations under dynamic artesian water[J]. Chinese Journal of Geotechnical Engineering, 2017, 39(2): 295-300.
[10]	CONTE E, TRONCONE A. Soil layer response to pore pressure variations at the boundary[J]. Géotechnique, 2008, 58(1): 37-44.
[11]	CAVALERA L. Consolidation under cyclic variation of boundary pore pressure[J]. Rivista Italiana Geotecnica, 1977, 11(4): 187-205.
[12]	刘凯，文章，梁杏，等. 一维低渗透介质非达西渗流实验[J]. 水动力学研究与进展A辑，2013, 28(1): 81-87.
	LIU Kai, WEN Zhang, LIANG Xing, et al. One-dimensional column test for non-Darcy flow in low permeability media[J]. Chinese Journal of Hydrodyna-mics, 2013, 28(1): 81-87.
[13]	DENG Y E, XIE H P, HUANG R Q, et al. Law of nonlinear flow in saturated clays and radial consolidation[J]. Applied Mathematics and Mechanics, 2007, 28(11): 1427-1436.
[14]	HANSBO S. Consolidation equation valid for bothDarcian and non-Darcian flow[J]. Géotechnique, 2001, 51(1): 51-54.
[15]	李传勋，徐超，谢康和. 考虑非Darcy渗流和应力历史的土体非线性固结研究[J]. 岩土力学，2017, 38(1): 91-100.
	LI Chuanxun, XU Chao, XIE Kanghe. Nonlinear consolidation of clayed soil considering non-Darcy flow and stress history[J]. Rock and Soil Mechanics, 2017, 38(1): 91-100.
[16]	刘忠玉，闫富有，王喜军. 基于非Darcy渗流的饱和黏性土一维流变固结分析[J]. 岩石力学与工程学报，2013, 32(9): 1937-1944.
	LIU Zhongyu, YAN Fuyou, WANG Xijun. One-dimensional rheological consolidation analysis of saturated clay considering non-Darcy flow[J]. Chinese Journal of Rock Mechanics and Engineering, 2013, 32(9): 1937-1944.
[17]	时刚，刘忠玉，李永辉．循环荷载作用下考虑非达西渗流的软黏性土一维流变固结分析[J]. 岩土力学，2018, 39(Sup.1): 521-528.
	SHI Gang, LIU Zhongyu, LI Yonghui. One-dimensional rheological consolidation of soft clay under cyclic loadings considering non-Darcy flow[J]. Rock and Soil Mechanics, 2018, 39(Sup.1): 521-528.
[18]	张文生. 科学计算中的偏微分方程有限差分法[M]. 北京：高等教育出版社，2006: 245-249.
	ZHANG Wensheng. Finite difference methods for partial differential equations in science computation[M]. Beijing: Higher Education Press, 2006: 245-249.