Seismic analysis of shallow tunnel collapse mechanisms with the horizontal slice method
To present analytical method to evaluate tunnel collapse mechanisms during earthquakes at another angle, seismic solutions are established based on the horizontal slice method and the variational principle. Different sliding surfaces are applied for comparison and the finite difference method is employed to verify the analytical results. Then, we conclude that it is conservative to leave out the vertical force and regard the static earth pressure as the horizontal stress at vault section. The curve sliding surfaces are more reasonable than the linear sliding surface and the safety factors on a sliding surface change widely during earthquakes. Furthermore, the curve sliding surface, with 2 undetermined constants and taking into account the different locations of the start point, is reasonable to analyze the shallow tunnel collapse mechanisms, and the analytical results have excellent agreement with the numerical simulation and previous studies. By parameter analysis, it shows that the tunnel depth, radius, friction angle and cohesion have an obvious influence on the sliding surface distribution, and the tunnel radius and cohesion are the two most important factors influencing the tunnel stability. Reducing the tunnel radius and increasing cohesion are the most useful ways to enhance shallow tunnel stability during earthquakes.
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