Influence of Filter Tube of Pumping Well on Groundwater Drawdown during Deep Foundation Pit Dewatering

Xuehan Zhang,Yeshuang Xu,Xuwei Wang

doi:10.3390/w13223297

Abstract

The partial penetrating waterproof curtain combined with pumping wells is widely applied to deep foundation pit dewatering engineering. The filter tube of the pumping well plays a critical role on the environment effect that resulted from foundation pit dewatering. This paper investigated the impact of the filter tube on the groundwater drawdown outside the pit to provide a theoretical basis for the foundation pit dewatering design. Three patterns according to the relative position of the waterproof curtain and the filter tube, which are called wall-well patterns, namely the full-closed pattern, part-closed pattern, and none-closed pattern, have been analyzed. By taking a practice engineering case in Shanghai as an example, the relationship among the proportion of the filter tube length to the dewatering aquifer thickness, the buried depth difference of the wall-well, and the groundwater drawdown difference at both sides of the waterproof curtain are discussed by numerical simulation. The full-closed pattern is the optimal wall-well pattern on the ideal condition. The suggested and optimal values of the filter tube length to the dewatering aquifer thickness are 38.7% and 58.2%. The suggested and optimal values of the buried depth difference of the wall-well are −6.41 m and −1.92 m.

Highlights

The aim of this paper is to integrate the theoretical basis for the design of a filter tube in foundation pit dewatering and give suggestions for the wall-well setting in engineering practice, especially in deep aquifers of Shanghai
The position and length of the filter tube is controlled by factors such as the permeability coefficient of the aquifer, groundwater replenishment conditions, design requirements for groundwater drawdown, and environmental conditions around the foundation pit
The position and length of the filter tube is controlled by factors such as the This papercoefficient investigated the impact the groundwater drawdownconditions, outside the design pit by permeability of the aquifer,ongroundwater replenishment the filter tube of the pumping well

Summary

Introduction

The groundwater basin of Shanghai is a typical multi-aquifer-aquitard system (MAAS). Groundwater control is essential for the foundation pit construction in Shanghai to avoid the risk of pit bottom gushing and flowing sand that resulted from the confined aquifer rich of groundwater [7,8,9,10,11]. Foundation pit dewatering with the combination of a waterproof curtain and pumping wells (wall-well) is generally used to ensure the stability of the foundation pit bottom [12,13,14,15]. The use of a full-penetrating waterproof curtain can block the groundwater connection between the inside and outside of the foundation pit, which can effectively reduce the groundwater drawdown and ground settlement outside the pit [16,17,18,19]. Compared with a fully cut-off waterproof curtain, the partial penetrating waterproof curtain is adopted widely during the construction of the foundation pit due to the constraints of construction technology, cost, or the surrounding environment [20]

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