Strata Responses Due to Pumping from Deep Confined Aquifers of Multi-Aquifer-Aquitard System in Shanghai

doi:10.16183/j.cnki.jsjtu.2021.386

Abstract

Abstract:

When pumping in confined aquifers, vertical leakage could be found in the multi-aquifer system in soft deposits, and the responses of groundwater flow and strata deformation are complicated. Based on pumping tests in an ultra-deep underground project, this study performs a 3D finite-difference modeling to investigate the responses of groundwater and strata to pumping in the second and third confined aquifers. It considers the hydro-mechanical coupled and small strain stiffness characteristics of soils in the analysis, and discusses and compares the spatiotemporal distribution characteristics of drawdown and deformation induced by pumping in different confined aquifers. The results indicate that the ground settlement induced by pumping in the second confined aquifer is greater though the groundwater drawdown is smaller, and the compression of dewatering aquifers caused by dewatering in the second and third aquifers accounts for 56.18% and 77.69% of the settlement, respectively. It could be attributed to the connectivity between the second confined aquifer and its overlying aquitards, which results in a greater influential depth. In addition, the compressibility of shallow strata is significantly greater than that of deep strata. The study is significant for the dewatering construction and environmental deformation control of ultra-deep excavations.

Key words: deep artesian water, pumping tests, groundwater flow, strata deformation, spatiotemporal distribution

CLC Number:

TU42

PENG Chenxin, LI Mingguang, ZHEN Liang, LI Yaoliang, ZHANG Zhebin. Strata Responses Due to Pumping from Deep Confined Aquifers of Multi-Aquifer-Aquitard System in Shanghai[J]. Journal of Shanghai Jiao Tong University, 2023, 57(2): 138-147.

Figures/Tables 13

Fig.1

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Tab.1

Fig.4

Tab.2

Soil layers and parameters used in analysis

土层编号		γ/ (kN·m^-3)	c'/ kPa	φ'/ (°)	ψ/ (°)	e	$E 50 r e f$ / MPa	$E o e d r e f$ / MPa	$E u r r e f$ / MPa	$G 0 r e f$ /MPa	γ_0.7	k_h/ (cm·s^-1)	k_v/ (cm·s^-1)
Aq0	②₁	18.5	6	26.5	0	0.93	5.31	4.43	31.00	124.0	2.7×10^-4	1.19×10^-6	7.76×10^-7
	③	17.5	2	29.6	0	1.18	3.61	3.01	21.04	84.2	2.7×10^-4	1.04×10^-6	6.78×10^-7
AdI	④	17.0	3	27.9	0	1.34	2.90	2.41	16.88	67.5	2.7×10^-4	1.94×10^-7	1.41×10^-7
	⑤₁	17.6	4	30.5	0	1.13	4.05	3.38	23.623	94.5	2.7×10^-4	3.77×10^-7	3.12×10^-7
	⑤₃	17.9	5	31.6	0	1.01	5.55	4.62	32.38	129.5	2.7×10^-4	2.42×10^-6	1.47×10^-6
AdII	⑧₁	18.0	8	32.4	0	1.01	5.70	4.75	33.26	133.1	2.7×10^-4	1.15×10^-6	7.32×10^-7
	⑧₂	18.7	8	33.1	0	0.85	6.75	5.63	39.38	157.5	2.7×10^-4	3.72×10^-6	2.31×10^-6
AqII	⑨₁	19.6	0	31.5	1.5	0.66	14.66	14.66	58.64	293.2	2.7×10^-4	3.01×10^-4	2.03×10^-4
	⑨_2-1	20.4	0	37.5	7.5	0.53	15.69	15.69	62.76	313.8	2.7×10^-4	1.00×10^-4	9.61×10^-5
	⑨_2-2	20.4	0	36.5	6.5	0.52	17.21	17.21	68.84	344.2	2.7×10^-4	4.98×10^-4	2.04×10^-4
AdIII	⑩	20.0	19	31.6	0	0.64	12.51	10.42	72.95	291.8	2.7×10^-4	2.05×10^-7	8.59×10^-8
	⑩_夹	19.5	0	32.0	0	0.71	9.25	7.70	53.93	215.7	2.7×10^-4	2.31×10^-5	3.47×10^-6
	⑩_A	19.5	0	37.0	7.0	0.69	12.37	12.37	49.48	247.4	2.7×10^-4	3.47×10^-4	7.98×10^-5
AqIII	11	19.5	0	36.0	6.0	0.69	15.40	15.40	61.60	308.0	2.7×10^-4	8.45×10^-4	1.74×10^-4
	11_T	19.2	0	36.0	0	0.76	10.78	8.98	62.87	251.5	2.7×10^-4	8.43×10^-6	4.68×10^-6
AdIV	12	20.1	15	30.0	0	0.62	12.20	10.17	71.19	284.8	2.7×10^-4	2.01×10^-7	1.18×10^-7

Tab.2

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序号	时间	试验内容	抽水井号	平均流量/(m³·h^-1)
1	2017-10-23T10:30—2017-10-29T19:00	初始水位观测	-	-
2	2017-12-7T12:20—2017-12-8T12:20	11层单井抽水	K11-1	75.30
3	2017-12-10T13:30—2017-12-12T16:30	⑨层单井抽水	K9-2	456.00
4	2017-12-20T12:00—2017-12-27T12:00	11层群井抽水	K11-1、K11-2	74.36、132.56
5	2018-1-2T 15: 00—2018-1-9T 16:00	⑨层群井抽水	K9-1、K9-2	146.70、452.20