Study on Dynamic Evolution of Overburden Rock Movement and Mining-Induced Stress of Ultra-high Working Face

Abstract

In order to explore the dynamic evolution of overburden rock movement and mining-induced stress of an ultra-high working face, taking the ultra-high working face of a 2# thick coal seam in a shallow mine field as the engineering background, this paper analyzes the distribution characteristics of principal stress, mining stress evolution characteristics, overburden rock migration characteristics, and overburden rock caving characteristics of a shallow overburden rock ultra-high working face under different advancing distances and calculates by FLAC3D numerical simulation software. The results show that when the working face advances to 200 m, the stress concentration degree presents a stable trend. The concentration degree and variation gradient of the maximum principal stress are greater than those of the minimum principal stress, while the range of the peak ahead coal wall is smaller than that of the minimum principal stress peak leading coal wall. With the increase of the advancing range, the stress recovery degree gradually increases, and the maximum principal stress recovery degree is higher than the minimum principal stress. When the working face advances to 300 m, the maximum principal stress restores to 66% of the initial value, while the minimum principal stress is only restored to about 50%, and the surface subsidence degree reaches 2.5 m.