Risk Assessment of Tunnel Face Instability under Multi Factor Coupling Based on Conditional Probability and Tunnel Construction Mechanics

The factors leading to the collapse of tunnel face are diverse, and there is an interaction relationship between multiple influencing at physical mechanical level. By analyzing coupling affecting instability working face, this paper deduces calculation method effect construction risk for a certain event based on conditional probability theory, makes reasonable assumptions monitoring data probability. Finally, it verified by model test. results show that have other or changing parameters surrounding rock, in which amplification will significantly change failure carrier, so unfavorable stability face. cause increase extrusion deformation. Even if causes small deformation increment, can also make transition grade unstable, collapse. research quantitatively evaluate predict process construction.