Proposing allowable volume loss caused by the combined effects of excavation and groundwater depression for risk management of adjacent buildings

Abstract

There are two primary causes of the ground movement due to urban tunnelling. The first one is lost ground and the second one is groundwater depression. Due to tunnelling, the adjacent structures can be damaged in extreme conditions that not only include excavation in soft ground but also the water bearing conditions that can lead to groundwater depression. The phenomenon of groundwater depression can change the characteristics of settlement trough obtained due to excavation. It is of importance to comprehend the maximum volume loss value above which the adjacent buildings could be vulnerable to damage. The main objective of this study is to investigate the allowable volume loss based on trough parameters in different excavation and groundwater conditions that could be used for the risks management of adjacent buildings. Fluid flow analysis was performed in order to analyze various effects of groundwater conditions on settlement troughs. In view of the previous empirical methods which consider the factors like tunnel depth to diameter ratio and volume loss, a prediction method was developed, based on numerical simulations, which could also consider the reduced pore pressure. Furthermore, while revising the modified Gaussian curve, a new curve was suggested in order to consider the groundwater depression. Based on the suggested prediction method, the allowable volume loss caused by the combined effects of excavation and reduced pore pressure was proposed to be used for the risks management of adjacent buildings.