Stratified Settlement Characteristics of the Soil Strata in Shanghai due to Dewatering

Abstract

Dewatering-induced ground settlement is an important issue, and there a cumulative effect in stratified soil settlement. Detailed research of the stratified soil settlement devotes to a better evaluation of ground settlement. To better investigate the dewatering-induced stratified settlement characteristics of the soil strata in Shanghai, an intensive field-monitoring program was carried out for the excavation of an underground metro station, which involved the dewatering of confined aquifers in urban areas. Analyses of monitoring results suggest that the groundwater tables dropped steadily. The ground settlement decreased with an increasing distance from the excavation, and the maximum ground settlement was less than the allowable value. The results for stratified settlement monitoring showed that the ground settlement was less than the settlement at the bottom of the soft soil clay layer, which indicates that the clay layer swelled during dewatering in the underlying soil layer. This special phenomenon, referred to as dewater-caused soil expansion, has not been reported in the existing literature. This project acts as a special case study and provides a basic insight into this phenomenon.