Numerical Investigation of Prefabricated Utility Tunnels Composed of Composite Slabs with Spiral Stirrup-Constrained Connection Based on Damage Mechanics

This paper investigates prefabricated utility tunnels composed of composite slabs with a spiral stirrup-constrained connection, considering material nonlinearity with concrete damage. An experiment was set up based on the prototype of a practical utility tunnel project, and the results were compared with finite element (FEM) simulation results with reasonable agreement obtained. The parametric analysis was carried out considering variations of seam location, haunch height and reinforcement, and embedment depth, using FEM simulations. It is found that, as with the increase in seam distance above haunch, the load capacity increases slightly, while the ductility does not vary much. The haunch height is not found to have an apparent effect on stiffness, load capacity or ductility. The increase in the embedment depth can enhance both the yield and peak loads while decreasing the ductility. A simplified method is proposed for evaluating the seismic performance in terms of deformation coefficient considering ductility demand, based on three different methods for calculating interaction coefficients considering soil–structure interactions. The findings from this investigation provide theoretical and practical guidance for underground engineering design of prefabricated utility tunnels.