Earthquake effects on tunnel floating slab track and lining with slab bearing and base isolator

Abstract

Earthquake is one of the biggest natural phenomena that causes damage and loss of life. Malaysia is prone to seismic tremors originating from nearby countries such as Indonesia and Philippines. The Sumatran earthquake in 2005 has raised questions about the structural stability and integrity in Malaysia including tunnel structures, given the substantial seismic effect from Sumatran earthquake. In addition, the waves that pass through soil medium would affect the behaviour of subsurface structure in tunnels. The scope of this study focused on Klang Valley Mass Rapid Transit (KVMRT Sungai Buloh – Kajang Line) in Malaysia. Rubber based isolators were inserted underneath the floating slab track of the tunnel to study the effectiveness of the isolated installation under earthquake loading and to identify the functions of the base isolator system used for the floating slab track of a tunnel. The finite element analysis of the individual base isolator conforms to the experimental laboratory testing under compression and shear loads. In order to verify the results of structural analysis, the finite element analysis was carried out for the base isolator under static analysis approach. Meanwhile, the tunnel floating slab track was modelled using finite element method (FEM) under dynamic analysis approach. Time history analysis was performed with peak ground acceleration to the structure to study the behaviour of tunnel lining and performance of floating slab track. From the results, it is found that the base isolator performed very well in reducing the seismic response of acceleration on floating slab track with a reduction of 17% from the actual acceleration. Moreover, the results have shown a slight reduction of tunnel lining internal forces if a base isolator is used on floating slab track. It can be concluded that a base isolator on floating slab track tunnel is recommended for human comfort and safety under earthquake effects.