Abstract:

With the Western China development, more and more larger and deep karst tunnel will be constructed with the risk of water inrush and mud gushing in the Western China karst area; and the model and type of water inrush are so complex for the uncertain attribute of concealed water body, such as its position, scale, etc.; and the risk coefficient is very high for the tunnel face. Under the effect of especially big water bearing structure, water inrush of tunnel face happens when the excavation face enters into the minimal distance of safety thickness; and the catastrophe characters of water inrush are obvious. According to the catastrophe phenomenon, the effect of construction condition on the catastrophe characters of water inrush has been analyzed by the numerical method. With the hypothesis of circular tunnel, a fold catastrophe model of water inrush for tunnel face instability has been established; the criterion condition and minimal safety thickness have been given through analyzing the total potential energy function of tunnel face structure; based on the analysis of evolution path of catastrophe controlling parameters, the measures for preventing water inrush have been put forward, of which the feasibility has been proved with an engineering example of water inrush.

Key words: karst tunnel, water inrush induced by tunnel face instability, catastrophe model, water inrush criterion, minimal safety thickness