急倾斜特厚煤层巷道非对称变形机理

Asymmetric seformation mechanism of roadway at steeply inclined thick coal seam

针对急倾斜特厚煤层回采巷道出现的非对称变形破坏,采用现场实测、力学建模计算及数值模拟揭示了急倾斜煤层巷道开挖后非对称变形破坏机理,分析了巷道开挖后应力场及塑性区分布特征,提出了可缩性U型钢与非对称性预应力锚杆(索)支护的全新支护加固方案。研究表明:(1)巷道非对称破坏表现为坚硬岩层侧帮部沿层理下沉、滑移、内扩,煤体侧帮部挤出帮臌;坚硬岩层侧顶部下沉量大于煤体侧,巷道中轴线偏向煤体侧;(2)巷道发生非对称的变形机理为:在非均布载荷的作用下,巷道两侧肩角支座反力的倾角及大小发生变化,坚硬岩层侧支座反力大于煤体侧,倾角为煤体侧大于坚硬岩层侧,坚硬岩层侧帮部在小角度大应力作用下沿层理滑移、下沉、内扩,煤体侧帮部在近乎垂直角度作用力下使帮部煤体挤出帮臌;(3)巷道从坚硬岩层侧向煤体侧弯矩一直增大,剪力呈现为先增大后减小再增大的趋势,且在二次增大时方向改变,方向改变处即为巷道轴线向煤体侧的偏移位置,轴力呈现为抛物线形式的先减小后增大,在非均布载荷作用下的巷道最优合理断面即为"非对称三铰斜拱";(4)提出可缩性U型钢与非对称性预应力锚杆(索)支护,重点加强巷道煤体侧帮部及坚硬岩层侧顶部支护。

In view of the asymmetrical deformation failure in the mining roadway at a steeply inclined special thick coal seam,some field observations,mechanical modeling calculations and numerical simulation analysis were used to reveal the asymmetrical deformation failure mechanism after the excavation of the roadway in steeply inclined coal seams.The stress field after the excavation of the roadway and the distribution characteristics of the plastic zone were analyzed.A new support and reinforcement scheme for the retractable U-shaped steel and asymmetric prestressed anchor(cable)support was proposed.The study shows that:①the asymmetrical failure of the roadway is characterized by the subsidence,slippage,and internal expansion along the bedding of the hard rock strata along the side of the coal body;the subsidence of the top of the side of the hard rock is greater than that of the coal side and the central axis of the roadway inclines to the coal side.②The asymmetric deformation mechanism of the roadway is that,under the effect of non-uniform load,the angle and size of the counterforce of the shoulder angle support on both sides of the roadway are changed.The reaction force of the hard rock lateral support is greater than that of the coal side.Also the inclination angle of the coal side is larger than the side of the hard rock.The side rock of the hard rock layer slides,sinks,and expands along the bedding under the action of small angle and large stress,and the side of the coal body is pushed out of the drum under the action of nearly vertical angle force.③The bending moment of the roadway from the side of the hard rock to the side of the coal body is increasing all the time.The shear force appears to increase first,then decrease and then increase,and the direction changes in the second increase.The position of the direction change is the offset position of the roadway axis inclining to the side of the coal body.The axial force appears as a parabola,decreasing first and then increasing.The optimum and reasonable section of the roadway under non-uniform load acts is the“asymmetric three-hinged arches”.④The retractable U-shaped steel and asymmetric prestressed anchor(rope)support are proposed,focusing on reinforcing the lateral support of the roadway coal body and the top support on the side of the hard rock.