In-site surveying and study on development laws of surface cracks by high-intensity mining in Shangwan Mine

In Shangwan Mine of Shendong Mining Area,coal seam occurrence is stable with small dip angle,large thickness smaller mining depth. With the adoption of wide working face and large-height fully-mechanized mining technology,the influence of high-intensity mining on surface environment is also more severe. Therefore, a high-intensity mining impact on the surface environment.In order to master the development rules of surface fractures under the geological and mining conditions of th is mine,the surface fractures in the observation area of 1 km on the side of the incision in the process of advancing the No. 12401 working face were measured. The obs ervation scheme of the surface cracks in different directions was designed. The trajectory of the cracks was measured by hand-held GPS ,the width of the cracks was m easured by steel ruler and the depth of the cracks was measured by iron rod. Three months later,the distribution information of 2 303 fractures in the observation area a t the side of the incisor was obtained. The results show that:①Four types of the surface fractures in the geological mining conditions of the mine,including stretching,c ompression,step and collapse ,and their zoning distribution,are analyzed and determined.②The periodic development rules of the surface fractures and the distributio n rules concentrated in the goaf range are obtained,and the main parameters of the fracture distribution are determined. The measured crack spacing is about 10 m,the maximum width of the crack is 0.7 m,the maximum depth is about4 ~ 10 m,the maximum length is 298 m,the maximum step height is0.45 m,the strike crack angle of th e side of the incision is 76.0° ,the up-dip crack angle is 86.0° ,and the down-dip crack angle is84.7°. ③During the process of advancing along the strike of the working fa ce,the main fractures that are distributed vertically with the direction of advancing occur periodically on the surface ,and they undergo a development process of " produ ction-expansion-compressionstability" for about 14 days. The width of the main fractures is greater than 50 mm,the spacing is about 129 m,and the lag angle is79.8° ~ 87.10. Based on the measured study of mining surface cracks in No. 12401 working face of Shangwan Mine,a basis for a scientific evaluation of surface mining damag e under the geological mining condition of the mine was provided.