Seismic Effect on Underground Box Structure for Metro and Subways with Varying Soil Parameters

Abstract

With the advancement in technology, urban transportation systems have been modernized with the construction of underground structures due to restricted movements and inadequate space. Many cities already have or plan to construct underground box structures for metros and subways. These structures may undergo severe damages caused by excessive deformation due to seismic shaking. Hence, it is necessary to have an accurate estimation of deformation and bending moment caused by the movement of the surrounding soil under seismic conditions. In the present investigation, an attempt has been made to carry out a parametric study for a typical box structure 9.6 m wide × 5.8 m high with varying soil parameters from loose to medium, medium to dense and very dense in different seismic zones. The results of the study reveal that about 16–26% of the variation in distortion and 8–12% of the variation in bending moment occur with different subsoil conditions (loose to medium, medium to dense and very dense) under the same seismic conditions. Once seismic conditions change from lower to higher seismic zone (zone-III to zone-IV), the deformation becomes almost double even for the same soil condition (loose to medium or medium to dense or very dense). The findings of the present study may be useful in the design of underground subways and metro box structures for practicing engineers.