Nonlinear Analysis of the Static Performance of Double-Chamber U-Shaped Assembled Utility Tunnel Under Circumferential Loading

The upper and lower prefabricated U-shaped components are connected by prestressed tendons at the construction site to form a prefabricated U-shaped assembled utility tunnel. This type of tunnel offers convenient transportation and installation， a short construction period， and minimal environmental impact. A finite element model of the U-shaped assembled utility tunnel was established using the commercial software ABAQUS， and its validity was verified through a circumferential loading test on a single-chamber U-shaped assembled utility tunnel conducted in an earlier study. Based on this model， a nonlinear analysis of the entire loading process of a double-chamber utility tunnel under circumferential loading （simulating earth pressure and top overload） was carried out. The parameters investigated included： utility tunnel type （cast-in-place vs. prefabricated）， lateral earth pressure coefficient （0.55， 0.65， and 0.75）， and effective prestress of the prestressed tendons （400， 500， and 600 MPa）. The finite element analysis showed that， unlike cast-in-place utility tunnels， plastic hinges in prefabricated tunnels first appeared at the mid-span of the top and bottom slabs， then at the junctions between the slabs and the middle wall， and finally at the joints of the side walls， leading to structural failure. The bearing capacity and ductility of prefabricated tunnels were higher than those of cast-in-place tunnels （by 2% and 33%， respectively）. Compared to the tunnel with a lateral earth pressure coefficient of 0.55， the bearing capacity of tunnels with coefficients of 0.65 and 0.75 increased by 6.4% and 11.75%， respectively， while ductility decreased by 2.3% and 18.6%. The effective prestress level of the prestressed tendons had little effect on the bearing capacity and ductility of the tunnel. Overall， the double-chamber prefabricated U-shaped assembled utility tunnel has high bearing capacity and good ductility， offering broad prospects for engineering applications.