EXPERIMENTAL STUDY ON WATER-INRUSH MECHANISM OF TUNNELS IN KARST AREA

摘要

The instability of karst ground water under the disturbance of external force always results in the geological hazard of water outburst and mud gushing. It is a dynamic damage phenomenon of water and mud flowing to the tunnel face with high speed. Based on the water-rock interaction mechanism in karst tunnel, the mechanism of water inrush has been analyzed by several model tests and the theory of karst geology, engineering hydraulics and rock mechanics. It is shown that the occurrence and formation of water outburst has two steps. The first step is that the karsls water and its pressure have softening and dissolution effect on rock. It has been qualitatively studied through hydraulic fracturing experiment on rocklike material. The second step is that the water flow and its pressure have passageway expanding and flowing yield controlling effect on water inrush. It has been analyzed through the similarity test. Based on the failure characteristics of water inrush experimental tests, a mechanical model of water inrush is put forward, and the analytic solution of critical protection thickness of rock mass preventing water inrush is given. This model can be used to the calculation of safety rock mass thickness.