坚硬顶板破断冲击机理及支架与围岩“收敛-约束”耦合机制研究

Dynamic impact mechanism of hard roof strata and coupling mechanism of “constrain-convergence” between support and surrounding rock

为研究坚硬顶板动力破断下支架与围岩的冲击响应,建立了基本顶架前破断动载冲击力学模型,开展了顶板冲击效应及煤壁稳定性三维相似模拟试验。研究结果表明:1)支架初始增阻期间,顶板平缓下沉,下沉量为5.5mm;煤壁变形不明显。2)支架"横阻"期间,顶板阶梯式下沉,下沉梯度达3.9mm;煤壁裂隙发育且屈曲明显。3)随着支架阻力的增阻和屈服,顶板对应地平稳变形和剧烈下沉,支架和围岩"收敛-约束"耦合特性明显。4)试验结束时,顶板最大下沉量为42.7 mm;煤壁发生大面积片帮,煤壁上部和中部水平位移分别为0.60和0.35 mm。5)当煤壁刚度较大或直接顶较软弱时,有助于缓解支架阻力;支架刚度与支架阻力呈正相关,提高支架刚度有利于降低煤壁压力和控制基本顶回转。

In order to study the impact response of the support and surrounding rock under the hard roof strata, an impact mechanics model of dynamic loading ahead of the main roof has been developed. A three-dimensional simulation experiment of roof impact effect and coal wall stability have also been carried out. The results have shown that during the slow resistance increase from the initial support, the roof deflects steadily. The vertical displacement of the roof reaches only 5.5 mm before the first impact loading with inconspicuous horizontal deformation in the ribs and only a few cracks. During the roof impact loading, however, the resistance of the support presents the cyclic change rule of "yield-increased resistance". the roof deflects in a step function with an incremental of 3.9 mm. Coal face fractures and buckles dramatically with noticeable horizontal displacement. Face fall occurs when the support is "yield-increased resistance" for the 8 th time, and the maximum roof deflection reaches 42.7 mm. The horizontal displacement of the face at the top and middle positions is 0.60 and 0.35 mm, respectively. With the slow increase of the resistance of the support and sudden drop in the yield, the roof convergence shows a steady increase and a sharp subsidence accordingly and the shield and surrounding rocks present clear "constrain-convergence" coupling characteristic. A stiffer coal seam or a weaker immediate roof may help mitigate the shield loading. And increasing the shield stiffness, which is positively correlated with the resistance of the support, can reduce the pressure on coal face and also control the rotation of the main roof block.