Comparative study on seismic performance of prefabricated and cast-in-place underground structures under different site conditions

Abstract

Since the seismic performance of prefabricated underground structures is not yet clear, they not have been constructed in high seismic intensity areas or poor sites. This paper aims to study the applicability of rectangular prefabricated (semi-rigid prefabricated, ASF, and rigid prefabricated, AMT) underground structures in soft soil sites located in high seismic intensity areas. The structures were compared with cast-in-place (CIP) underground structures. Three-dimensional soil-structure interaction advanced finite element models were established to simulate the seismic behavior of the three types of underground structures (ASF, AMT and CIP) constructed in two different sites (soft rock site and soft soil site). The pre-earthquake stress states, dynamic responses, and post-earthquake performance states of the three underground structures were systematically analyzed, considering various static and dynamic conditions. Additionally, the results of dynamic time history were compared with those of the standard procedures available in the literature. The results demonstrated that: i) site conditions have a significant effect on the structures’ static and dynamic responses, ii) the seismic response in soft soil site is much larger than that in soft rock site, but the ratio of response of prefabricated underground structures to that of CIP is almost the same for both soft soil and soft rock sites. Furthermore, as the peak ground acceleration increases, the percentage difference of inter-story displacement ratio (IDR) between ASF, AMT and CIP underground structures in soft soil site decreases, and iii) prefabricated underground structures can be used in both soft rock and soft soil sites. In addition, the seismic performance of ASF is better than that of the AMT structure, which is better than that of the CIP structure. However, when the ASF structure is built in a site with high seismic intensity and poor soil conditions, special consideration must be given to waterproofing measures for wall-slab joints or setting up tongue and groove to improve the connection stiffness and reduce the deformation.