A Numerical Study on Parameters Affecting Seismic Behavior of Cut and Cover Tunnel

Abstract

Underground structures and facilities constitute the underlying and infrastructural part of modern urbanization and are used for a wide range of applications, including urban underground railroad and urban road tunnels, silos etc. Underground structure’s construction method depends on such factors as the ground conditions, the ground water conditions, the tunnel span and the buried depth. The cut and cover method is an engineering technique for underground construction with low buried depth in urban areas. Furthermore, some urban underground facilities have been constructed in areas with risk of seismic activity which be resistant to both static and seismic loads. Therefore, seismic response of such shallow tunnels which are usually constructed by cut and cover method is of great importance and is investigated in this paper. Numerical analyses were performed on a shallow tunnel subjected to S-wave by using FLAC software, and the effects of different parameters are investigated. The maximum forces and bending moments in the tunnel lining during the earthquake motion for two earthquakes i.e., Tabas and Gilroy were compared and it was found that at all levels of maximum acceleration of input motion, seismic forces on tunnel structures during the Tabas earthquake were more critical which is related to the Arias intensity of the input motion. Increasing the buried depth of shallow tunnel and the enlargement of the tunnel span lead to more seismic forces on tunnel structures. Furthermore, with the increasing rigidity of the tunnel to the surrounding soil, additional dynamic forces in the tunnel lining will be more, however the stresses in the tunnel lining are reduced.