Mechanical behaviors of “easy cracking zones” of precast rectangular utility tunnels

In this study, a single tubular section of the rectangular utility tunnel project in Shenyang city, China was simulated by applying a Finite Element Method. To increase the simulation accuracy, reinforcing steel bars were practically added to the utility tunnel model. Using the equivalent static loading method, the potential failure modes of rectangular utility tunnel at different buried depths were equivalently modeled by changing the imposed loads on the roof and side wall. Uniform pressure was applied on the top surface of roof, and a linear change in lateral earth pressure was extended on the external surface of side wall. Two tensile stress concentration zones were observed on the top surface of the roof, and one tensile stress concentration zone was observed on the external surface of side wall, easily leading to cracking on the surface concrete of these zones. These tensile stress concentration zones are named as “easy cracking zones” in this study. The effect of span size and corner type of rectangular utility tunnel on the easy cracking zones was then studied; the results provide a theoretical reference for the future design of rectangular utility tunnels.