LAUSR

The excavation of the rock mass will have a great influence on the characteristics of the caverns under extremely bad geological conditions. According to the characteristics of the engineering geology, several groups of the caverns are designed to be excavated in the rock mass with three sets of through joints. Based on the summary of the failure mechanism and the failure pattern, the classification method of the failure modes is done for the flat large-span underground cavern with three sets of through joints. The classification method takes into account the control factors of the surrounding rock instability, failure mechanism, distribution of the disturbed zone, and characteristics of the rock weakness, etc. The failure modes of the flat large-span caverns contain six types: the relatively stable, the partial area falling, and the partial collapse of vault, the zigzag failure of rock stratum, the V-shaped failure, and the large-scale collapse. The change law of the vertical stress is first increasing and then decreasing for the surrounding rock in the disturbed zone. The horizontal stress shows an exponential change trend with an increase in the distance from the vault. Influenced by the failure degree of the caverns, the change law of the vertical displacement for the vault can be divided into two types. The horizontal displacement decreases with an increase in the distance from the sidewall, and there is an exponential relationship between them.