EXPERIMENTAL STUDY ON OUT-OF-PLANE SEISMIC PERFORMANCE OF SIDEWALL CONNECTIONS OF UTILITY TUNNELS WITH COMPOSITE PLATES

The utility tunnel with composite plates is a semi-assembly structure, which has the advantages of fewer joints, superior impermeability and good application prospect. To investigate the seismic performance of the composite plate sidewalls of utility tunnels with grouting-sleeve connection and rebar lapping in grout-filled hole connection under out-of-plane loads, a series of low-cycle repeated tests were performed on the full-scale sidewall specimens with two types of connections in this study. The experimental results are compared with those from the cyclic tests of the cast-in-place sidewall of the utility tunnel. By investigating the failure modes, crack distributions and mechanical performance indices of differ specimens, the influence of different connections on the out-of-plane seismic performance of the composite plate sidewall is preliminarily revealed. The test results show that the seismic performance of the composite plate specimen is basically the same as that of the cast-in-place specimen. The hysteresis curves, the ultimate bearing capacity and stiffness degradation law are all similar, which meets the seismic design requirement of prefabricated structures being equivalent to cast-in-place structures. The ductility coefficients of the two types of composite plate utility tunnel sidewall specimens are 7.05 and 8.50. Both specimens exhibit excellent out-of-plane ductility and meet the deformation capacity requirements in seismic design code. Compared with the composite plate specimen connected by grouting sleeve, the hysteresis curve of the composite plate specimen connected by rebar lapping in grout-filled hole is plumper with better deformation capability, but the ultimate lateral loading bearing capacity is smaller, and the damage is more serious under the same lateral displacement. Besides, both types of connections can effectively transfer the reinforcement stress until the failure of the sidewall specimens.