Abstract: The water disease of highway tunnel in karst area caused by rainfall often occurs, which seriously affects the safety of tunnel operation. Hence, in order to further clarify the formation mechanism and adverse effects of this kind of water disaster, the geological exploration and water connectivity test are carried out in Yangpeng Tunnel on Beijing- Zhuhai Expressway. And then the characteristic of stress field and seepage field of the tunnel under high water pressure after rain are explored through numerical simulation method, and countermeasures are put forward. The results show that: (1) The main causes of the water disease are heavy rainfall, karst strata and water infiltration channel, and the high external water pressure caused by the above-mentioned reasons is the direct cause of the disease. (2) Due to the lack of drainage capacity, the tunnel structure, especially in the bottom and crown, still bears high water pressure, which greatly weakens the safety of the lining structure and is easy to cause cracks in the sidewall and the bottom of the tunnel. (3) The renovation measures of new discharge chamber + surface plugging and drainage + new discharge hole in sidewall are adopted, and the applicable effect is good.

Key words: expressway tunnel, water disease, karst, high-density electrical method, water connectivity test, numerical
simulation