Abstract: For the karst tunnel with pipeline cavity in the surrounding rock, it is very easy to accumulate high water pressure in the pipeline cavity due to the influences of heavy rainfall on the surface and groundwater, which will lead to lining cracking, water leakage and water gushing diseases. To explore the influence of high water pressure on the lining structure, a model test of pipeline karst tunnels under high water pressure was carried out, and the internal force characteristics of tunnel lining under the influence of cavity position and head height were studied. Based on this, the numerical calculation model of extended working conditions was established. The effects of cavity diameter, cavity position and water head height on the lining structure were further explored. The results show that the inner side of the lining in contact with the cavities bears larger positive bending moment, when there are karst cavities around the tunnel, which are the most unfavorable stress positions of the lining. The internal force of the lining increases greatly, with the increase of cavity diameter and water head height in the cavity. The location of the cavity affects the internal force distribution of the lining, and the anti-water pressure capacity of the lining is the smallest, when the cavity is located at the tunnel vault. The research results can provide reference for the structural design and safe construction of pipeline karst tunnels.

Key words: karst tunnel, pipeline cavity, model test, numerical simulation, internal force of the lining