Combined cut and cover and new Austrian tunnelling methods for MRT station in Bangkok sub-Soils

Abstract

Ground and wall movements in an excavation using a combined cut-and-cover method and New Australian Tunnelling Method (NATM) for an MRT station is studied by means of a 2D finite element analysis. An advanced elasto-plastic constitutive law is adopted to model the soil behavior. Multi-stage construction of both the cut-and-cover box and NATM excavation are modeled. Ground surface settlements behind diaphragm walls induced by the cut-and-cover excavation are in good agreement with those calculated from the simplified method. Deflection of diaphragm wall on the NATM excavation side was smaller than that of the opposite side due to stress release from the tunnel excavation. However, ground surface settlements increased three times of the settlement occurring after the excavation of the cut-and-cover box.