浅埋超大采高工作面覆岩裂隙演化及能量耗散规律研究

Fracture evolution and energy dissipation of overlying strata in shallow-buried underground mining with ultra-high working face

为研究浅埋超大采高工作面覆岩裂隙演化及能量耗散规律,以上湾煤矿为研究背景,基于相似模拟实验,数字图像处理、分形理论和数值模拟,分析了8.8 m超大采高工作面采动覆岩裂隙演化及能量耗散规律。研究表明:伪顶垮落到亚关键层阶段、亚关键层破断到主关键层阶段和主关键层破断到完全垮落阶段,关键层破断前后覆岩裂隙分形维数呈上升-稳定-下降趋势;依次可划分为3个阶段;依据充分采动后裂隙发育形态可将采场覆岩划分为6个区域:垮落裂隙区、离层压实区、离层裂隙区、竖向破断裂隙Ⅰ区(垮落区后方)、竖向破断裂隙Ⅱ区(工作面后方)、Ⅱ区离层裂隙区,其中竖向破断裂隙Ⅰ、Ⅱ区是张剪混合型发育,裂隙角度范围0°~90°,离层裂隙区覆岩层裂隙发生张拉型扩展发育,张拉型裂隙,裂隙倾角角度范围300°~360°,垮落区裂隙发育形态复杂,裂隙角度范围值大,贯通性好;建立了覆岩裂隙分形维数与耗散能量的关系;数值模拟得出裂隙发育高度与采高和工作面推进距离拟合公式。研究成果可为神东矿区超大采高开采覆岩裂隙发育规律研究提供参考。

The fracture evolution and energy dissipation of overlying strata in shallow-buried underground mining with ultra-high working face are complex issues in mining researches.In this paper,the evolution of fractures and the energy dissipation of overlying strata in a shallow-buried longwall face with 8.8 m ultra-mining height at Shangwan coal mine were analyzed through similar simulation experiment,digital image observation and processing,fractal calculation and numerical simulation.The results showed that there three stages of fractal dimension variation of fractures in overlying strata during the mining.The fractal dimension will increase during the stage of false roof collapsing to the sub-critical stratum,then the fractal dimension will keep stable during the sub-critical stratum breaks to the main critical.The fractal dimension will drop down as the main critical stratum breaks to the complete collapse.The overlying strata above stope can be divided into six zones according to the fracture development pattern after full mining:caving fracture zone,separation compaction zone,separation fracture zone,vertical fracture zone I(behind the caving area),vertical fracture zone II(behind the working face),and separation fracture zone II.The vertical fracture zones I and II are full of the mixed development of tension and shear fractures,and the fracture angles range from 0 to 90°.The overlying strata fracture zone in the separation fracture zone is mainly caused by tensile stress,and the inclination angle is from 300°to 360°.The fracture development in the caving zone is complex,and the fracture angle has large range variation and is easy to be connected.The relationship between fracture fractal dimension and energy dissipation in overlying strata is established,and the fitting formula of fracture zone height,mining height and retreat mining distance is obtained by numerical simulation.The results could provide a reference to the similar investigations on the strata movement caused by the shallow-buried underground longwall mining with ultra-high working face at the Shendong coalfield.