Abstract: To investigate the mechanical response characteristics of a tunnel lining structure under the condition of a sharp increase in the water pressure in pipetype hidden caverns, numerical simulations are performed here using the finite difference software FLAC3D to analyze the force changes and damage characteristics of the lining. Additionally, the effectiveness of the numerical method is validated through similar indoor model tests. Furthermore, numerical models for the actual expansion conditions are constructed to examine the effects of the cavity location, cavity dimension, and water pressure on the internal forces of the lining structure. The results reveal the following aspects: (1) When the cavity is located at the crown, the internal force and displacement of the lining increase in an "Sshaped" manner with increasing water head in the cavity. Moreover, the water pressure is 1.35 MPa when the lining is damaged by water leakage under the test working condition. (2) Various cavity locations differently affect the internal force distribution of the lining. Furthermore, when the cavern is located at the crown, the waterpressure resistance decreases by 0.3 MPa compared with those at the sidewall and bottom, indicating the smallest waterpressure resistance of the lining structure. (3) Under the same waterpressure conditions, the internal force of the lining considerably increases with increasing cavity size, and thus the influencing scope of the cavity broadens.

Key words:  , karst tunnel, pipetype hidden cavern, high water pressure, internal force of lining, model experiment, numerical simulation