Optimized back-analysis for tunneling-induced ground movement using equivalent ground loss model

Abstract

Application of an optimization technique for the back-analysis of tunneling-induced ground movement is presented in this paper. The conjugate gradient method was adopted for the optimization procedure and the gap parameter model was utilized to evaluate the ground movement. According to the results of back-analysis using the monitoring data of the Taipei Rapid Transit System, the angle of the influence zone of ground settlement is approximately 45° for tunneling in clayey soils, and that for sandy layers ranges from 30 to 50°. Backfill grouting will reduce the physical gap of shield machine in the order of 60–80% for tunneling in clayey soils and in the range of 70–85% for sandy layers. Semi-empirical equations were established to predict the tunneling-induced ground movement in the silty clay and silty sand of Taipei basin. Case studies were presented to demonstrate that the adoption of the method can provide a reasonable prediction of the ground settlement due to shield tunneling.