Experimental study on the vertical deformation of aquifer soils under conditions of withdrawing and recharging of groundwater in Tongchuan region, China

Abstract

Land subsidence due to aquifer-system compaction accompanying groundwater extraction is a global hazard. Rising urban construction and groundwater demand necessitate increased awareness and better understanding of the geological problem. Motivated by the lack of laboratory-scale studies on this issue, an experimental investigation on the newly developed Tongchuan region, China, is presented. The study addresses the deformation behaviors of three soil samples, with the lithology of silty clay, silt, and fine sand, under the conditions of groundwater withdrawal and recharge using the GDS Consolidation Testing System. Results indicate that all three samples were characterized by elastic-plastic deformation under the conditions of withdrawing and recharging. The vertical deformation of the silty clay in the aquitard above the first confined aquifer was larger than those of the other two samples, and its deformation is a gradual and long process; thus, considerable attention should be paid to deformation in this aquitard due to the apparent creep effect and tiny rebound deformation. However, the settlement of the fine sand in the second confined aquifer cannot be ignored due to the great thickness of the aquifer. For the same soil, as the pore-water pressure declined, the unit rate of vertical deformation decreased gradually, whereas the creep effect of deformation in the later declining stage of pore-water pressure was more apparent than that in the former declining stage. These observations are highly important to the local government, which is developing measures to prevent and control subsidence.

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

“…The experiment conducted in this paper is verified to be reliable. It has been successfully applied in the newly developed area of Tongchuan region, located north of Xi'an city, Shaanxi Province, where land subsidence becomes a serious geological problem since 2000 due to the over exploitation of groundwater [3]. The experiment can also be applied to other regions to simulate the groundwater withdrawal and recharge.…”

“…Land subsidence due to groundwater extraction is a consolidation process that causes a decrease in pore water pressure and an increase in effective stress [43]. In this study, the GDS Consolidation Testing System, developed by Global Digital System Ltd, was used to simulate the change in pore water pressure during the consolidation process in soil samples based on a one-dimensional model [3]. The upper chamber and back-pressure controllers were selected to impose pressures p 1 and p 2 externally and internally on the samples, as shown in Fig 3 . The pressure p 1 represents the total stress acting on the samples in the original strata, and the pressure p 2 represents the pore water pressure (u) inside the sample.…”

“…Land subsidence induced by groundwater withdrawal has been a worldwide problem [1][2][3], and more than 60 countries around the world are facing issues associated with this problem [4]. Land subsidence usually leads to damage to the aquifer system, decrease in water quality, and destruction of subsurface and surface structures, such as underground tunnels, buildings, roads, railways and pipelines [5][6][7][8][9].…”

Mechanism of loess planar erosion and numerical simulation based on CFD–DEM coupling model

“…One of the most abundant powders to support each other to form the skeleton particles (aggregate), a mixture of clay and salt formation pore filling the skeleton particles, as cement skeleton particles closely connected or in a loose area in the form of "bridge" connect skeleton particles, constitutes the loess special columnar joints and big pore structure built on stilts, This kind of porous and loose characteristic is convenient for hydraulic erosion of loess. Based on the analysis of a large number of electron microscope photos and literature review, this paper obtained the following three main unit structure forms of loess microscopic fabric Sun et al, 2021;Wei et al,2017;Liu et al, 2004): a bare core (silt) + cement; b core (powder) + coat + cement; c aggregate (fine powder + cement = aggregate, i.e. aggregate); The three forms are shown in Fig.…”

Groundwater Chemistry Regulated by Hydrochemical Processes and Geological Structures: A Case Study in Tongchuan, China

“…Knowledge of hydrochemical processes of groundwater can provide an effective approach to protect, treat, and restore contaminated groundwater [11,12]. Previous studies examined the geological-hazards and groundwater pollution sources [9,10,13,14], however, the hydrogeochemical processes in Tongchuan remain unknown. The geologic structure is complicated, with two faults cross-cutting the study area.…”