煤层厚度与层间岩性对上保护层开采效果的影响研究

采用数值分析的方法,建立了保护煤层开采厚度、被保护煤层赋存厚度及层间岩性对上保护层开采保护效果影响的计算模型。结果表明,当上保护煤层开采厚度增加但小于下部被保护煤层赋存厚度,或者上保护煤层开采厚度不变而被保护煤层赋存厚度增加时,保护效果逐渐增加;但当上保护煤层开采厚度大于被保护煤层赋存厚度时,保护效果基本一致。同时,当上保护煤层与下部被保护煤层间的岩层岩性越硬时,被保护煤层煤体单元的塑性变形量和应力减小量越小,保护效果越差。在实体煤岩内,岩性差异大的区域内水平应力降也较大。采空区下方不均衡分布的垂直应力的垂向挤压与水平应力的横向剪切作用,是底板煤岩体单元发生偏心失稳进而产生塑性变形和破坏的重要原因。

Research on the upper protective coal seam mining effect induced by coal thickness and interburden rock properties

Based on numerical simulation, a new model has been established on the effectiveness of protective mining due to the influence of the mining thickness of the upper protective coal seam, the thickness of the protected coal seam, and interburden rock strata properties. The results have shown that if the mining thickness of the upper protective coal seam increases but still is less than the occurrence thickness of the lower protected coal seam, or if the occurrence thickness of the protected coal seam in-creases but the mining thickness of the upper protective coal seam remains the same, the protective ef-fects will increase gradually. But once the mining thickness of the upper protective coal seam is larger than the occurrence thickness of the protected coal seam, the protective effect will not change basically. Furthermore, the harder the interburden rock stratum between coal seams is, the less the plastic defor-mation and stress reduction of the lower protected coal units will be, and therefore the worse the protec-tive effect will become. Finally, the stress reduction would be larger if the differences of the neighboring rock stratum are large in coal and rock mass, and both the longitudinal squeezing caused by imbalanced vertical stress and the transverse shearing caused by imbalanced horizontal stress are the important pre-cipitating factors that lead to the eccentric instability of coal and rock units under the gob and then result in the plastic deformation and failure.