| ABSTRACT:The karst water inrush in the tunnel construction has become one of the most serious engineering disasters. This paper will focus on karst water inrush geological disasters during the present tunnel construction, based on YiWan railway tunnel project at typical karst area, by investigating the local hydro geological conditions and engineering geological conditions and analyzing karst geological data. This paper analyzes the main influencing factors, the karst hydrodynamic profile zoning, the sudden flood characteristics and the failure mode of karst water inrush. This paper establishes a numerical model simulation of tunnel excavation when the karst cave is located at the front of the tunnel face to determine the stability of surrounding rocks. The main conclusions are:(1) The larger diameter of karst cave, the closer distance between tunnel and karst cave, and the greater water pressure inside the cave are more unfavorable to the stability of the tunnel surrounding rock. In contrast, the location of karst cave and the water pressure have more influence on the tunnel structure. When the distance between the karst cave and tunnel is more than a certain value, the tunnel structure caves the size of the impact of change on a relatively small number.(2)The failure modes of karst water inrush are divided into the water-sealing rock columns, the shearing failure of the fissures, the hydrodynamic expansion of the fissures, and the stability-losing failure of the block.(3)According on columnar type of shear failure and the shear strength of impermeable rock pillars, this paper calculates the size of safe thickness relying on the balance formula. |
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