NUMERICAL SIMULATION ANALYSIS OF DEFORMATION IN COAL CAVITIES BASED ON FLAC^3D

The paper selected the goaf located at Xinhua-Ying'an section of planned Dandong-Altai National Highway as the engineering background. We established the goaf model based on a finite difference software(FLAC^3D)to study the deformation pattern of the overburden layer and ground surface under geostatic stress. We also obtained the stress-strain pattern in the mining process. The analysis results show that the original geological state is changed due to the exploitation of underground coal seams. The maximum principal stress occurs at the boundary of the goaf and the roof, and obvious stress concentration occurs. In the upper part of the roof, the maximum principal stress gradually increases from the top to the bottom, and compressive main stress is predominant. Settlement deformation and failure are most likely to occur at the roof of goaf, and the vertical displacement increases with the reduction of the distance to the top of the goaf and vice versa. The vertical displacement of the rock formation with the away from the goaf is gradually reduced. The subsidence basin is asymmetrical. The maximum displacement of the surface subsidence occurs at the downhill side of the middle of the subsidence basin. The settlement displacement reaches a maximum value of 791 mm after the mining of the multi-level goaf. We calculated the maximum settlement value of the study area by the theoretical calculation of the probability integral method, and the calculation result is 830 mm, which is consistent with the result got by FLAC^3D numerical simulation method.