Singapore tests NATM at Fort Canning

This article describes the implementation of the New Austrian Tunneling Method (NATM) for an excavation in Singapore’s Fort Canning Hill area. In addition to being the first mined road tunnel in Singapore, this tunnel will also be the largest soft ground NATM-dug tunnel in the world. With a number of geotechnical factors in mind, excavators proceeded in their work using a back-actor excavator with hydraulic chisel attachments for the large boulders (but with the exclusion of road headers or explosives). For tunnel support the contractors used a systematic pipe roof arch and wet mix shotcrete. The tunnel will be finished as a totally hydrostatic sealed environment, without drainage or channeling allowances. The mechanical and electrical contract for this tunnel was awarded for US$5 million and will involve a series of longitudinal jet fans for emergencies.