Cross passage mining in highly permeable and soft ground

Abstract

Over the last 2 decades, there is a huge development in Singapore’s Rail Infrastructure projects. Downtown Line 2 (DTL2) is part of this major rail network. This paper will focus on the construction of 4 mined cross passages work for one of the contract under DTL2. As the cross passages were located in very high permeable soft ground condition mining for the cross passages pose huge challenges. In addition, the allowable settlement in this project was very stringent as the construction was located underneath a busy 6 lanes road with congested utilities. The construction was also in close proximity to high rise residential area. This paper will discuss the construction difficulties encountered on site related to face stability, basal heave, water ingress and the distortion of cross passage lining and how these construction difficulties were overcome during construction stage without causing major impact to the surrounding road, utilities and building structures.