唐山沟矿厚层砂岩顶板切缝沿空成巷试验研究

Research on cut gob-side entry retaining in thin coal seam of Tangshan ditch

垮落带内含有厚层坚硬岩层时,难以冒落,易在沿空巷道采空区侧形成弧形三角悬板,对沿空巷道产生较大压力。以大同唐山沟8820厚层砂岩顶板首采面无煤柱开采为背景,分析普通充填留巷和切缝沿空成巷侧向顶板断裂结构特征及围岩稳定过程,认为对垮落带内直接顶坚硬层顶板进行合理参数下的切缝,可使得切缝高度范围内采空区边界直接顶和基本顶失去约束,并沿切缝结构面剪切破断充分冒落接顶,降低破断冲击动载;并通过UDEC数值模拟软件,分析出切缝有利于矸石冒落并支撑上覆岩层,可将上覆基本顶岩层的触矸点前移,限制基本顶回转和下沉作用引起的围岩压力,明显减小巷道围岩变形量。基于理论、数值分析研究结果,确定唐山沟矿8820回风巷巷内加强巷旁密集支柱+巷旁双向聚能爆破切缝的上压下支中间切缝的联合切顶方案。通过井下爆破参数试验、矿压监测分析,评价切顶成巷的效果。井下试验表明:顶板高恒阻大变形锚索、巷内加强巷旁密集支柱、巷旁密集档矸点柱、超前聚能切缝爆破的切顶成巷综合技术,能够有效切落沿空巷道侧向顶板并形成完整巷道,各项指标均满足下一工作面回采要求。

The triangle hanging plate is easily formed and hard to fall if the caving zone contains the thick and hard stratum,which produces high pressure to the gob-side entry retaining. The 8820 coalface mining without pillars with the thick and hard sandstone roof at Tangshangou in Datong was studied. The difference of cracked structural feature between ordinary filling entry retaining and joint-cutting gob-side entry retaining roof was analyzed. The deformation process of surrounding rock was investigated. The joint-cutting with the reasonable parameter of hard stratum roof in the caving zone resulted in the lost of the constraint of the direct roof and basic roof at the gob-side boundary in the range of the joint-cutting height. The hanging plate was sheared enough to fall off the roof along the structural surface of joint-cutting,and the impact load was reduced. The results of the numerical analysis with the software UDEC indicated that the joint-cutting was beneficial to the waste rock fall and supported the stratum covered above. The joint-cutting moved forward the touch point of the waste rock of the stratum covered above basic roof,limited the rotation of the basic roof and the pressure of surrounding rock caused by the sink action and reduced the deformation of the surrounding rock obviously. The test under the well suggested that the complex techniques of high constant resistance and large deformation anchor rope of roof,the dense pillar reinforced on the side of tunnel,the dense block rock point pillar and the technology of advanced focused power blast of joint-cutting could cut the roof on the gob-side effect and form a complete tunnel that every index could satisfy the requirement of working surface.