STUDY ON GROUND BEHAVIOUR ASSOCIATED WITH TUNNELLING IN MIXED-FACE SOIL CONDITION

Abstract

Underground tunnel passing through mixed-face soil conditions become one of the most challenging demands in urbanized tunnelling works. A sudden change in soil medium at the tunnel face creates difficulties in controlling face pressure and over excavation that can cause substantial ground loss and movements. This thesis focused on the study of ground behaviour associated with closed-face tunnelling in mixed-face soil condition. To understand the soil behaviour due to bored tunnelling in mixed-face soil conditions, field performance study was conducted on one of the Downtown Line-3 MRT projects in Singapore, C933 Bendemeer Station. Numerical back-analyses were then performed on the measured field data using 3-D finite element software. Subsequently, the important factors influencing the soil behavior such as different face pressure application and different soil types at interface were discussed. Based on the studies and findings, recommendations on face pressure and expected volume losses for different mixed soil conditions were established.