复合采动损伤对层间隔水控制层稳定性的影响

近距离煤层群复合采动影响下,层间岩层中隔水层的稳定性至关重要。若层间岩层中隔水层的稳定性遭受破坏,则上覆采空区中的积水会向下方渗流扩逸,甚至瞬间涌出,威胁下部煤层的安全开采。提出了复合采动影响下层间隔水控制层的基本概念,运用损伤力学的基础理论构建了复合采动影响下层间岩体损伤参量D的计算模型,分别研究了损伤参量D与层间岩体抗压强度及破坏范围之间的关系,分析了不同条件下复合采动损伤对层间隔水控制层稳定性的影响。研究结果表明:(1)层间隔水控制层是指复合采动影响下层间岩体中不发生破断失稳且能起到阻隔上方采空区积水向下渗流扩逸的控制岩层。(2)损伤参量D可以用来衡量复合采动影响下层间岩体的损伤破坏程度。(3)层间岩体抗压强度R_D与损伤参量D的关系为:随着损伤参量D的增大,层间岩体的抗压强度R_D表现出线性递减的变化趋势,其折减系数为1-D。(4)层间岩体破坏范围与损伤参量D的关系为:层间岩体的最大破坏深度/高度H_(max)及其距工作面端部的距离L_(max)均随着损伤参量D的增大而增加;D越大,H_(max)和L_(max)的增幅也越大。(5)层间隔水控制层的稳定性与复合采动产生的叠加损伤密切相关;通过综合考量上下煤层多重开采后层间岩体的损伤破坏范围与隔水控制层的层位关系,全面分析了6种不同条件下层间隔水控制层的稳定性,并给出了合理有效的控制措施,来减轻上覆采空区积水对下部煤层开采的威胁,并保障安全生产。复合采动损伤对层间隔水控制层稳定性的影响研究可以为积水采空区下伏煤层的安全开采提供理论指导。

Influence of multiple mining damage on the stability of water-resisting control strata

The stability of sandwiched water-resisting strata plays a significant role in the closed multiple-seam mining.The upper accumulated water in the upper gobs can seeped and flow into the lower mining space once the stability of sandwiched water-resisting strata is destroyed.In some situations,a sudden release of upper accumulated water is occurred,which brings serious threats for the safe mining of lower coal seam.The basic concept of water-resisting control strata under the influence of multiple mining was proposed in this paper.The damage parameter (D) calculation model of interburden was established based on theories of damage mechanics.The relationships between the damage parameters (D) and the compressive strength/the damage range of interburden were analyzed,respectively.Then,the influence of multiple mining damage on the stability of water-resisting control strata was investigated.The results showed that ① The water-resisting control strata referred to the strata which did not broken under the multiple mining influences and played a significant role in preventing the downward seepage and expansion of accumulated water in the upper gobs.② The damage parameter (D) could be used to measure the damage range of interburden under multiple mining influences.③ The relationship between the compressive strength (RD) of the interburden and the damage parameter (D) was: RD of the interburden showed a linear decreasing trend with the increasing of D.The reduction factor was 1-D.④ The maximum failure depth/height (Hmax) and the maximum distance to the working face (Lmax) increased with the increase of damage parameter (D).The larger the damage parameter (D),the greater the increase of Hmax and Lmax.⑤ The stability of water-resisting control strata was closely related with the superimposed damage induced by the multiple mining.It was necessary to comprehensively evaluate the damage range of interburden under the multiple mining of upper and lower coal seams.The stability of water-resisting control strata under six different conditions were determined and the reasonable control measures were then complemented to ensure the safety of lower coal seam mining.The study on the influence of multiple mining damage on the stability of water-resisting control strata can provide a theoretical guidance for the safe mining of lower coal seam under the water accumulation area.