Analysis of disaster mechanism and influence of water inrush in tunnel construction under complex environment
Water inrush is one of the common geological hazards in tunnel construction,which seriously threatens the safety of tunnel construction.Based on the case of water inrush in tunnels passing through reservoirs and fault tectonic zones,this study systematically analyzed the causes of disaster caused by water inrush in tunnels from the perspectives of geological characteristics,surrounding rock disclosure,geological radar detection,and water inrush morphology.On this basis,a tunnel water inrush analysis model was established,and the calculation formula for the safe critical thickness of tunnel water inrush was deduced based on the limit equilibrium theory and seepage theory,and a criterion for the stability of tunnel water inrush was proposed.Based on the single factor variable method and grey correlation method,the influence mechanism of tunnel water inrush was revealed.The results show that:1)The essence of the tunnel water inrush is that there is a small water-bearing cavity lurking in the tunnel arch.The tunnel excavation causes stress redistribution of surrounding rock and the release of groundwater energy.Under the action of dynamic water pressure and infiltration scour,coupled with the influence of excavation disturbance on the permeability coefficient of surrounding rock and seepage,the movement of fissure water induces the progressive seepage failure of small-scale pipe-type water inrush formed by the expansion and penetration of fissure channels;2)Three basic factors of disaster formation caused by water inrush in the tunnel were proposed:surface water collection,geological structure and seepage pressure;3)The critical safety thickness of the tunnel increases with the increase of water pressure of water-bearing cavity and the diameter of the crack channel,and decreases with the increase of cohesion.With the increase of internal friction angle,the influence of the critical safety thickness of tunnel is minimal.The sensitivity of influencing factors is sorted as follows:crack channel diameter>cavity water level>cohesion of filling medium>internal friction angle.The diameter of the crack channel has the greatest influence on the safety and stability of the tunnel.4)The research results provide a reference for understanding the mechanism of water inrush in tunnels and for prevention and control of water inrush in similar projects.
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