Reliability calculation method for stability of shield excavation face of gravel stratum

The invention discloses a reliability calculation method for stability of a gravel stratum shield excavation face. The reliability calculation method comprises the steps that a three-dimensional stratum model of gravel fragmentation rock stratum shield excavation based on Thiessen polygon is established; gravel fragmentation rock mass parameters are obtained, so that the joint parameter range of the gravel fragmentation rock mass parameters is obtained; according to the gravel fragmentation rock mass parameters and the three-dimensional stratum model, the safety coefficient of the shield excavation face is obtained; acquiring a training sample according to the orthogonal design scheme, and acquiring an inspection sample according to the uniform design scheme; the BFOA-LSSVM coupling model is trained, so that the mapping relation between the gravel fragmentation rock mass parameters and the safety coefficient of the shield excavation face is obtained; and the reliability probability is obtained, and the reliab