Study on Mine Pressure Control by Ground Fracturing High-level Hard Rock Strata

The high-level thick and hard strata are the main reason for the presence of a strong ground pressure during extra-thick coal seam mining, however, there is no active and effective control technology. This paper proposes the method of ground fracturing hard roofs, and the physical simulation was used to study the control effect of ground fracturing on the strata structure and energy release. The results showed that the ground fracturing changed the structural characteristics of the strata, reduced the energy release intensity and overburden movement spatial extent, which had a significant control effect on the ground pressure. The Datong mining area was selected as the engineering background, a ground horizontal well fracturing engineering test was conducted on site, and a 20-m-thick hard rock layer, which was 110 m vertically above from the coal seam, was determined as the fracturing target layer. On-site microseismic monitoring showed that the crack propagation length was up to 216 m, and the height was up to 50 m. On-site mine pressure monitoring showed that the roadway deformation was reduced to 100 mm, the periodic weighting characteristics of the hydraulic supports were not obvious, the ground pressure in the working face was significantly controlled, which proved the ground fracturing successful. Ground fracturing changed the breaking characteristics of the high-level hard strata, which is beneficial to ameliorate the stress concentration in the stope and provide an effective approach of hard rock control.