神东矿区遗留煤柱间隔岩层顶板破坏特征分析

Failure characteristics of retaining coal pillar interval rock formation roof in Shendong mining area

以神东矿区石圪台煤矿2^(-2)煤层为工程背景,对近距离煤层条件下工作面过上覆遗留煤柱顶板破断规律及控制技术进行研究。采用理论分析、数值模拟、现场实践等方法,分析了遗留煤柱下间隔层裂隙发育特征,阐明了工作面过上覆遗留煤柱3个阶段及其特点,揭示了工作面过上覆遗留煤柱强矿压产生的主要原因,提出了定向长钻孔水力压裂超前区域弱化治理思路并应用于现场实践。研究结果表明,由于上部“倒梯形”载荷结构作用,遗留煤柱在煤层底板会产生应力集中,导致间隔岩层易沿煤柱边界产生纵向下行裂隙,该裂隙对间隔关键层破断特征有一定影响;在下煤层开采过程中,可将工作面过煤柱划分为“进煤柱阶段”“煤柱中阶段”和“出煤柱阶段”,而“出煤柱阶段”是发生强矿压显现的主要阶段,提出了在该阶段进行水力压裂控制措施,在治理区域工作面来压步距降低9.8%,来压强度降低13.6%,动载系数降低10.6%。实践表明,水力压裂控制措施治理效果良好,研究结果可为该矿区后续工作面开采动力灾害治理提供借鉴。

Taking the 2^(-2) coal seam in Shibitai Coal Mine of Shendong mining area as the engineering background,the breaking law and control technology of the roof of the overlying retaining coal pillar over the working face under the conditions of close coal seam were studied.Using theoretical analysis,numerical simulation,field practice etc,the development characteristics of fractures in the lower interval layer of retaining coal pillar were analyzed.The three stages and characteristics of the overlying retaining coal pillar over the working face were clarified.The main reasons for the strong mine pressure of the overlying retaining coal pillar over the working face are revealed.The idea of weakening the advanced area of hydraulic fracturing in directional long borehole was proposed and applied to field practice.The results of the study show that:Due to the action of the upper “inverted trapezoidal” load structure,the retaining coal pillar will produce stress concentration in the coal seam floor.As a result,the interval rock strata are prone to longitudinal downward fractures along the boundary of the coal pillar.The fracture has a certain influence on the breaking characteristics of the interval key layer.In the process of mining in the lower coal seam,the coal pillar of the working face can be divided into “entering coal pillar stage”,“coal pillar middle stage” and “exiting coal pillar stage”.The “exiting coal pillar stage” is the main stage when strong mine pressure occurs.Hydraulic fracturing control measures are proposed for this stage.In the treatment area,the weighting step distance of the working face was reduced by 9.8%,the weighting strength was reduced by 13.6%,and the dynamic load coefficient was reduced by 10.6%.The practice that the hydraulic fracturing control measures are of good effect,providing a reference for the subsequent mining dynamic disaster management of the working face in the mining area.