Discussion of Goaf Critical Depth Calculation Methods under Freeway

Goaf critical depth is used to describe the influence of buried goaf on upper structures, that is to say, if the goaf burial depth is less than the goaf critical depth, the goaf must be emphatically treated, and if the burial depth is greater than the critical depth, but less than one and half of the critical depth, the goaf also need to be treated, and if the burial depth is greater than one and half of the critical depth, the goaf need no treatment. Nowadays, mechanic balance method has been using to calculate the goaf critical depth, which considers the upper rock as the loose structure, and the destroy plane is vertical. Based on the discussion of critical depth calculation methods, the critical depth calculation method thinking of the cohesive strength of the part upper rock was put toward. The method was applied to the goaf treatment engineering of Chengtang Freeway of Hebei province, and was proved by the monitor results. The critical depth calculation method can reduce the engineering quantity of goaf treatment.