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全支撑应力场下采场顶板损伤特征及释能估算

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

  • 摘要: 针对顶板突发性损伤释能诱发冲击地压的现象,以忻州窑矿11号煤层8518下工作面地质开采条件为工程背景,基于弹性理论建立涵盖煤壁支撑和支架支撑的采煤工作面顶板力学模型,对采场顶板损伤分布特征及释能估算进行研究,得到顶板损伤判据、损伤高度计算式以及释能引起的冲击压力表达式。结果表明:①采场顶板支撑状态可分为煤壁支撑区、支架支撑区和无支撑区。顶板应力呈非连续分布,在各区交界和顶板跨中出现集中,是顶板在支架前、后端及采空区出现拉、剪损伤的力学原因。②顶板损伤在煤壁支撑区、支架支撑区及无支撑区分别呈直角扇形、直角梯形和非对称直墙拱形,其范围受顶板悬露长度
    控制,悬露长度每增加10 m,损伤面积约扩大8.0%。支撑强度仅对支撑区损伤产生影响,支撑强度每增加1 MPa,支撑区损伤面积约缩小2.2 m2。③无支撑区损伤是顶板的主要损伤区,其损伤高度影响着损伤范围的大小。损伤高度主要受顶板悬露长度、顶板厚度和顶板内摩擦角控制,其与悬露长度和厚度呈线性增大关系,与内摩擦角呈线性减少关系。④顶板变形能密度高的分布区与顶板损伤区重合,顶板损伤面积每增加1倍,损伤释能增大1倍、释能引起的冲击压力增大2.8倍。研究成果为矿山围岩冲击振动响应及其稳定性分析提供可量化的力源值。

     

    Abstract: 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.

     

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