A Coupled One-Dimensional Numerical Simulation of the Land Subsidence Process in a Multilayer Aquifer System due to Hydraulic Head Variation in the Pumped Layer

Abstract

After exploitation of groundwater had been reduced and the groundwater level of the confined aquifer had risen, land subsidence was observed to continue rather than cease for several years according to the layer-wise mark monitoring data in Xi'an. To analyze the phenomena, a numerical model of a coupled one-dimensional multilayer aquifer system is developed to represent land subsidence due to hydraulic head variation in the pumped layer. The numerical simulation results show that the pressure head in other layers does not rise immediately when the hydraulic head in the pumped layer starts to recover after pumping ceases. In addition, after the pumping is stopped, a dividing point can be found in aquitards next to the pumped layer, with the aquitards being divided into two parts: a compressed part and a rebounding part. The dividing points move toward the side and away from the pumped layer with the transferring of pore pressure in the aquitard. The results of the simulation also show that there is a transition period between land subsidence and rebound. In this transition period, land could continue to subside even though the hydraulic head in the pumped layer begins to recover.

A One-Dimensional Fractional-Derivative Viscoelastic Model for the Aquitard Consolidation of an Aquifer System

“…where δ t is the Dirac delta function and t is the time. It is obvious that the substitution of equation 7into equation (6) gives the constitutive relationship of the linear elastic model if α = 0, while it produces that of the standard Merchant model if α = 1. That is, both the linear elastic model and standard Merchant model are two special cases of the fractional-derivative Merchant model.…”

“…In general, the bottom boundary of the aquitard connected to the nearly rigid sandy stratum yields zero deformation [29]; thus, the settlement of the aquitard can be obtained by integrating equation (6) along the vertical direction. The result is…”

“…Land subsidence including both gentle downward warping and the sudden sinking of parts of the ground surface is one kind of widespread geological disaster that occurs in many countries and regions all over the world [1][2][3][4][5][6][7]. In China, it has been found that land subsidence mainly occurred in 17 provinces in the eastern and central regions [5,6]. Commonly, land subsidence can result from natural processes (such as mineral dissolution), human activities, or a combination of both.…”

“…Luo et al [17] derived theoretical solutions for analyzing the settlement process resulting from decompression in an aquifer. Wang et al [6] studied the land subsidence process resulting from hydraulic head variation in a multilayer aquifer system. Zeng and Wang [18] deduced an analytical solution for studying the consolidation behavior of an aquifer system under unsteady groundwater variation.…”

Characterizing the Deep Pumping-induced Subsidence Against Metro Tunnel Using Vertically Distributed Fiber-Optic Sensing

“…Note a growing consensus has suggested that ground subsidence occurs lagging behind the pumping activity (Kearns et al, 2015), and the duration of land subsidence induced by deep pumping is longer than that by surface pumping (Cui and Jia, 2018). However, current theoretical models of the pumping-induced settlement remain unavailable to fully characterize the abovementioned influencing factors (Budhu and Adiyaman, 2010;Wang et al, 2018;Xu et al, 2012;Zhang et al, 2017;Zhou et al, 2017). Therefore, concerning extracting deep groundwater scenarios, current models still have to be deliberately calibrated by the field measurements (Shen and Xu, 2011;Xu et al, 2016a).…”