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Karst tunnels are usually faced with the risk of water disaster caused by seasonal fluctuation of water level in water-eroded groove. Due to seasonal precipitation, water supply and other reasons, water storage structures such as karst caves and underground rivers are in the state of low water level in the dry season. When the rainy season comes, the groundwater level rises rapidly due to water supply of these water storage structures, and water accumulates behind the tunnel lining through water-eroded groove or karst fissure (karst pore). The water pressure of tunnel lining increases sharply, which seriously threatens the safety of lining structure. Through relevant investigation, the authors learn that a heavy rainfall caused a section of lining to break, and this section had to be repaired during the construction of Yunwushan tunnel on Yiwan railway. Besides, during the construction of Yinshan tunnel in Guizhou Province, a rare rainstorm occurred, and the vertical side wall of the tunnel was crushed by sudden karst water, with the destruction length of the side wall reaching 20 m. Another example is when the construction of Jijiapo tunnel passed through the karst area in Hubei Province, the water pressure behind the lining increased sharply during the heavy rainstorm, which resulted in serious fracturing of the second lining and the bottom plate as well as water gushing due to bottom drum rupture of the construction joint. Macro influences of karst groundwater on tunnel lining structure have been studied by a large number of scholars through numerical simulation and field test. However, most of them are qualitative analyses insufficient in the study on external water pressure of tunnel lining in karst areas, and do not highlight the distribution characteristics of external water pressure of lining under fluctuating water level of water-eroded groove. Therefore, these studies can hardly reflect the actual influence of karst groundwater on lining structure in terms of the calculation with load-structure method. Based on the engineering case of a highway tunnel in the karst area of Southwest China, this study quantitatively analyzes, through numerical simulation, the influence of different groundwater levels and different locations of water storage in water-eroded grooves on the stress of tunnel lining. The research process is shown as follows. According to the results of geological exploration and groundwater connectivity test under on-site rainfall conditions, the typical cross-section of the tunnel was firstly selected. Subsequently, the external water pressure of tunnel at different water levels was calculated through seepage software, which was followed by the calculation of the surrounding rock pressure according to the specifications. Finally, the internal force of the lining was calculated through the "load-structure" method. According to the careful analysis and scientific judgment, the occurrence mechanism and evolution characteristics of the tunnel water hazard risk were revealed. The main conclusions indicate as follows. (1) The water level fluctuates in water-eroded groove under seasonal heavy rainfall, and the pressure of water outside the tunnel changes frequently, which results in significant changes of internal force of tunnel lining. When the water level rises, the structural stress increases and the safety will greatly reduce. The arch and side walls are still loaded in the mode of small eccentric compression, while the mode of loading at the bottom of the tunnel gradually develops from small eccentric compression to large eccentric compression. There exists the risk of cracking and breakage of lining structure at high water level. (2) The water storage of water-eroded groove at the side wall of the tunnel results in bias water load on the tunnel, and the safety factor of the side wall decreases by up to 1.1. The safety factor of tunnel lining at the same water level is less than that of the corresponding position on the other side, with the difference of safety factor between 0.1 and 0.3. With the gradual increase of groundwater level, the difference shows a decreasing trend, i.e. from bias water load to even water load, and the influence on structural force difference gradually reduces. (3) Under the condition of high groundwater level caused by seasonal heavy rainfall, although the tunnel drainage system has played a certain role of pressure relief, the tunnel lining still bears high water pressure. There is a possibility that the structural safety cannot be satisfied, especially at the side wall and the bottom of the tunnel. Therefore, when seasonal heavy rainfall comes, the drainage system should be conducted smoothly. Strengthening drainage and pressure relief is the key to the problem that excessive water pressure caused by water head rise will roughly destroy lining. Besides, the safety of lining structure of side wall and tunnel bottom should be paid close attention to. In this study, the numerical simulation is used to quantitatively analyze the stress response and difference of lining structure under the condition of water level fluctuation in water-eroded groove, so as to provide theoretical support for disaster prevention of karst tunnel. [ABSTRACT FROM AUTHOR]