A case study of twin bored tunnelling under mixed-face soil-Bendemeer MRT station project (Downtown Line 3), Singapore

Abstract

The Bendemeer Station project is part of the construction of MRT Downtown Line 3 (DTL-3) in Singapore, under Contract C933. High variation in geological condition along the alignment was encountered during the tunneling works in this project. The transitions from Old Alluvium soil towards the soft soils of Kallang Formation create the challenging mixed-face soil condition at the tunnel face. This sudden change of tunnelling medium creates the difficulties to control face pressure and over excavation which can cause substantial ground loss and movements. This paper mainly focuses on the ground responses caused by twin bored tunnelling under mixed-face soil condition and the implementation of building protection measures to the existing late 19th& early 20th centuries shophouses which the tunnelhad undercrossed in mixed-face soil condition.