Model Test Research on the Mechanical Characteristics of Tunnel Lining Structures under Local High Water Pressure in Concealed Karsts

Abstract

Mountainous karst areas contain many hidden karsts around highway tunnels. During the stormy rain season, concealed karsts connected to surface are recharged by surface water. Consequently, the water level of the corresponding caverns rises sharply, posing an imminent threat to the safety of the lining structure of the operating tunnel. This paper uses similar model experiment methods from a highway tunnel in southwestern China to discuss the contact pressure between the lining and surrounding rock, internal lining force, and change law of the failure mode when the local high water pressure acts on the sidewall. Results showed that at increasing external water pressure, the contact pressure between the lining and surrounding rock in the hydraulic pressure area decreased, whereas the contact pressure at other parts increased. Consequently, the axial force distribution maintained a “horseshoe shape” whose maximum value was proportional to the position of the external water pressure. Moreover, the pressure had a more dramatic influence on the bending moment of the lining that even changed its direction. Furthermore, the right side wall fractured when the water pressure acted on the left side wall, making the left side appear under the load. However, the longitudinal penetrating cracks were the same as the sidewall dislocation during the operation of the tunnel. These findings have specific reference significance for the design of traffic tunnels in karst areas.