STUDY ON JOINT ROTATION LIMITS OF UTILITY TUNNELS BASED ON FUNCTIONAL LIMIT STATES

Aiming at the problem of functional integrity of underground utility tunnel disturbed by adjacent engineering construction, Based on the assumption that rigid body rotation occurs in the section near the joint of a utility tunnel, the geometric relationship is established between the rotation of the utility tunnel joint and the detail geometries of the utility tunnel considering the water-proof failure at the joint, and the joint rotation limits is preliminarily investigated for the utility tunnels with different cross-sectional geometries corresponding to the water-proof failure. Based on the ultimate tensile and compressive strain of the internal pipelines of a underground utility tunnel, the joint rotation limits are also presented for the utility tunnel corresponding to the failure of internal pipelines with different diameters. The analysis results show that: the joint rotation limit corresponding to the water-proof failure of the utility tunnel is closely related to the configuration of the water proof material at the joint and the cross-sectional geometries of the utility tunnel; the water-proof failure of the utility tunnel joint plays a critical rule to the functional integrity of the utility tunnel when the width of the utility tunnel is less than 10 m and when the pipeline is smaller than the nominal diameter of DN500. Otherwise, when the width of the utility tunnel is more than 10 m and the pipeline is larger than DN500, the failure of internal pipelines occurs before the water-proof failure of the utility tunnel joint. Considering the two failure modes of water-proof failure and internal pipelines failure in the utility tunnel, the limited value of the joint rotation can provides a technical reference for the functional integrity and safety design of the utility tunnels.