Mechanical Property of Precast Slab-Assembled Utility Tunnel with UHPC Connections

A precast slab-assembled concrete utility tunnel connected by Ultra-High Performance Concrete （UHPC） consists of a base slab， sidewalls， and a roof slab， and the rebars protruding from the base slab are lap-spliced with the longitudinal reinforcement of the sidewall by UHPC. To study the mechanical properties of the precast slab-assembled concrete utility tunnel with UHPC connections， an overall model of the utility tunnel was established based on the commercial finite element software ABAQUS. A joint test of the utility tunnel was conducted to validate the model’s rationality. The failure modes， bearing capacity， and ductility of the specimens were in good agreement with the finite element calculation results. On this basis， a parametric finite element analysis was conducted， focusing on key parameters such as the axial compression ratio （0.05， 0.1， and 0.15） and the vertical location of the UHPC cast-in-place segment （at the base slab top surface， and 350 mm above it， and 500 mm above it）. The finite element analysis results showed that both precast and cast-in-place models failed due to sidewall flexure， with the bearing capacity of the precast model being 3% lower than that of the cast-in-place model. Compared to the utility tunnel with an axial compression ratio of 0， the bearing capacities of the models with axial compression ratios of 0.05， 0.1， and 0.15 increased by 11.6%， 15.4%， and 18.3%， respectively， while their ductility coefficients decreased by 2.4%， 5.4%， and 8.6%， respectively. The location of the UHPC cast-in-place segment had little effect on the overall bearing capacity and ductility of the utility tunnel structure. In general， the precast slab-assembled concrete utility tunnel with UHPC connections has good mechanical properties and shows broad prospects for engineering applications.