ABSTRACT
The DTSS Advance Tunnel has been constructed as an advance structure to the Deep Tunnel Sewerage System to avoid active mining underneath the tunnels of the new North East MRT Line, which would be operational at the time of the construction of the DTSS tunnel system. It was the first major NATM tunnel construction in Singapore’s Old Alluvium. The paper is dealing with both, design as well as construction aspects of this structure. Design approaches are presented to quantify the effects on the Advance Tunnel lining during the passage of the two EPB TBMs of the North East Line. The varying geometry of the access tunnel and its curved alignment required very good skills to control the excavation shape during construction. Predicted deformation values are compared with monitoring results gathered during the actual passage of the TBMs and details are given of plant and equipment used for excavation, shotcreting and ventilation.
