Experimental Study and Estimation of Groundwater Fluctuation and Ground Settlement due to Dewatering in a Coastal Shallow Confined Aquifer

Abstract

The coastal micro-confined aquifer (MCA) in Shanghai is characterized by shallow burial depth, high artesian head, and discontinuous distribution. It has a significant influence on underground space development, especially where the MCA is directly connected with deep confined aquifers. In this paper, a series of pumping well tests were conducted in the MCA located in such area to investigate the dewatering-induced groundwater fluctuations and stratum deformation. In addition, a numerical method is proposed for the estimation of hydraulic parameter, and an empirical prediction method is developed for dewatering-induced ground settlement. Test results show that groundwater drawdowns and soil settlement can be observed not only in MCA but also in the aquifers underneath it. This indicates that there is a close hydraulic connection among each aquifer. Moreover, the distributions and development of soil settlement at various depths are parallel to those of groundwater drawdowns in most areas of the test site except the vicinity of pumping wells, where collapse-induced subsidence due to high-speed flow may occur. Furthermore, the largest deformation usually occurs at the top of the pumping aquifer instead of the ground surface, because the top layer is expanded due to the stress arch formed in it. Finally, the proposed methods are validated to be feasible according to the pumping well test results and can be employed to investigate the responses of groundwater fluctuations and stratum deformations due to dewatering in MCA.

Coastal Geohazard and Offshore Geotechnics

“…Li et al [18] conducted a series of pumping well tests for the coastal micro-confined aquifer (MCA) in Shanghai to investigate the dewatering-induced groundwater fluctuations and stratum deformation. With the field tests, a numerical method is proposed for the estimation of hydraulic parameters and an empirical prediction method is developed for dewatering-induced ground settlement.…”

“…(2) evaluation of stability of marine infrastructures, including pipelines [6][7][8], piled foundation and bridge piers [9][10][11][12], submarine tunnel [13], and other supported foundations [14]; and (3) coastal geohazard, including submarine landslide and slope stability [15,16] and other geohazard issue [17,18]. More details of each contribution are summarized in the following subsections.…”

Numerical evaluation of a 70-m deep hydropower station foundation pit dewatering

“…For the limitation of laboratory experiments, in-site pumping and dewatering tests are usually performed to determine the hydraulic parameters of a dewatering engineering. In-situ pumping-recharge tests, single-well pumping and multi-well recharge test, and multi-well pumpingrecharge tests are carried out to verify the non-Darcy ow and feasibility of arti cial recharge in deep con ned aquifer (Wang et al 2013(Wang et al , 2014(Wang et al , 2017Zhang et al 2017aZhang et al , 2017bLi et al 2019). The data from eld measurement of excavation and support were analyzed to study the deformation law of adjacent building structures, surface settlement, displacement of supporting piles, axial force, and water level variation during different excavation stages of deep excavation construction .…”

Experimental study of land subsidence in response to groundwater withdrawal and recharge in Changping District of Beijing

“…However, few studies have used experimental methods to characterize and predict land subsidence. Li et al [36] performed field pumping well tests in the Pudong New Area of Shanghai to investigate the response of groundwater level and layer deformation. The results show that the soil deformation matches well with the groundwater fluctuation, and there is a close hydraulic connection between the pumping aquifer and the underlying aquifer.…”