Damage characteristics and energy release estimation of stope roof under fully supported stress field

In view of the phenomenon of rock burst induced by sudden energy release of damaged roof, taking the geological mining conditions of 8518 lower working face in No.11 coal seam of Xinzhouyao mine as the engineering background, based on the elastic theory, a roof mechanical model of working face with coal wall support and bracket support was established, and the roof damage distribution characteristics and energy release estimation were studied. Several formulas were derived including the roof damage criterion, damage height calculation formula and the expression of shock pressure caused by energy release. The results show that: ① The roof support state can be divided into coal wall support area, hydraulic pressure stand support area and unsupport area. The stress distribution of roof is discontinuous and concentrated at the junction of each area and in the middle of roof span, which is the mechanical reason for the tensile and shear damage of roof at the front and back of support and in the gob. ② The roof damage in coal wall supporting area, the hydraulic pressure stand support area and the unsupported area presents right angle fan, right angle trapezoid and asymmetric straight wall arch respectively, and its range is mainly controlled by the roof overhanging length. Every 10 m increase in overhanging length, the damage scope expands by 8.0%. The support strength only affects the damage of the support area, and the damage scope of the support area decreases about 2.2 m2 when the support strength increases by 1 MPa. ③ The damage of unsupported area is the main damage area of the roof, and its damage height affects the size of the damage scope. The damage height is mainly controlled by the overhang length, thickness and internal friction angle of the roof. The damage height increases linearly with the overhang length and thickness of the roof, and decreases linearly with the internal friction angle. ④ The distribution area with high energy density of roof deformation coincides with the roof damage area. Every time the roof damage area is doubled, the damage energy release is doubled and the impact pressure caused by energy release is increased by 2.8 times. The research results provide quantifiable force source values for the analysis of impact vibration response and stability of surrounding rock.