Abstract:  Utility tunnels are typically regarded as lifelines of a city, whereas the cracks of the utility tunnel structure affect the appearance, cause groundwater leakage, and reduce the durability of the structures and related equipment. In order to explore the causes of cracking of the utility tunnel of Fuzhou Southeast freeway in China, the settlement monitoring data of the utility tunnel during construction are analyzed, and the finite element method of crack propagation is used for numerical simulation. Conclusions are drawn as follows: (1) During the construction of the utility tunnel in the test section, the soil loss occurred in the foundation, resulting in the uneven settlement of the utility tunnel and the dislocation of deformation joints, which is the root cause of the utility tunnel cracks in the largemileage section. (2) After constructing the compacted concrete, an uneven settlement occurred in the large-mileage section, and the local tensile stress of the roof near section K3+917 in the middle of the utility tunnel exceeds the standard value of concrete tensile strength, resulting in roof cracks. (3) The deformation joints dislocated with the increase in the settlement difference of the utility tunnel on both sides of the deformation joint, causing water and sand gushing and the expansion of roof cracks toward the middle and sidewalls.

Key words: cast-in-place utility tunnel, uneven settlement, crack, extended finite element method