The First Circular Shaft in Asia with the Use of Vertical Shaft Sinking Machine
The population of Singapore has increased by three fold as compared to five decades ago. To cope with the population growth, more infrastructures are required and many of these will be constructed underground. The Deep Tunnel Sewerage System (DTSS) Phase 2 is a sewer network comprises of deep tunnels which transport domestic used water at western part of Singapore, by gravity to Tuas Water Reclamation Plant (WRP). With the completion of DTSS, existing intermediate pumping stations and conventional WRPs will be phased out, freeing up land. Under DTSS Phase 2 Contract T11, twenty one number of deep circular shafts connecting from ground levels to the tunnels are to be constructed. The shaft construction could be quite challenging as these shafts are located in highly permeable sand layer underlain by fractured rock and also in proximity to critical structures. In addition, these shafts are up to 45m deep which makes the construction programme and logistic handling even more challenging. The first ever vertical shaft sinking machine (VSM) in Asia is introduced for this project to overcome some of these challenges. This paper will present the design concept of VSM shaft and compare the benefits of VSM construction with typical circular shaft construction.