Finite Element Analysis of Composite Slab-Assembled Double-Cell Utility Tunnel with Bottom-Slab Protruding Rebars

The composite slab-assembled utility tunnel with bottom-slab protruding rebars consists of double-sided composite sidewalls， a single-sided composite roof slab， and a cast-in-place bottom slab. The sidewalls are connected to the bottom slab by reserved L-shaped protruding rebars. This type of utility tunnel has advantages such as good waterproof performance， fast construction speed， and good structural integrity. Based on the finite element analysis software ABAQUS， a finite element model of the composite slab-assembled utility tunnel with bottom-slab protruding rebars was established. To verify the accuracy of the model， a full-process loading test of a single-cell utility tunnel was carried out. The failure modes， peak bearing capacity， and lateral deformation obtained from the test were in good agreement with the finite element analysis results. On this basis， nonlinear mechanical analysis of the composite slab-assembled concrete double-cell utility tunnel with bottom-slab protruding rebars was conducted， focusing on the effects of haunch height （0 mm， 150 mm， 200 mm， and 250 mm） and axial compression ratio （0 to 0.1） on the structural performance. The results showed that the tunnel mainly exhibited flexural failure. Plastic hinges first formed at both ends of the inner sidewalls， then at both ends of the roof and bottom slabs， and finally at the joints between the outer sidewalls and the bottom slab. Increasing the haunch height significantly improved the peak bearing capacity， but reduced the ductility to some extent. The axial compression ratio had no significant effect on the peak bearing capacity， but led to a reduction in ductility. Overall， the composite slab-assembled concrete double-cell utility tunnel with bottom-slab protruding rebars showed good mechanical properties.