Abstract
This study proposes a pseudo-static procedure for investigating roof stability of deep-buried tunnels in non-uniform rock/soil surrounds, on the basis of a generalized nonlinear Mohr envelope and upper bound theorem. Non-uniformity of rock/soil surrounds is discretized to certain layers characterized by differing rock/soil properties. An effective collapse mechanism is constructed, satisfying an associated flow rule and the generalized Mohr envelope. After having computed the internal and external rates of work, the upper bound formulations including collapse profile, collapse height and width are derived based on work rate balance equation. FE modelling is simulated to verify the analytical solutions with and without considerations of vertical dynamic forces. Effects of corresponding parameters representing rock/soil properties and external forces are investigated to demonstrate the implication on tunnel roof stability, aiding to provide reference for design and engineering practice.
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