采场顶板关键层“横U-Y”型周期破断特征的试验研究

Experimental study on “horizontal U-Y” periodical breakage characteristics of key strata in stope roof

针对部分坚硬顶板矿井采动导水裂缝带处于8~15倍采高的高位关键层,"横O-X"破断运动引发工作面动载矿压甚至压架、临采空侧回风平巷超前100~200 m底鼓大变形等动力灾害的问题,采用自制的大尺度三维物理模拟实验平台,研究高位关键层的破断运动特征。结果表明:关键层发生横向破断时,首先,关键层板正面两侧长边和反面中部长轴方向同时形成破断裂隙;其次,关键层板正面两侧短边形成弧形裂隙,而反面沿中轴线端点同步形成八字形破断裂隙;再次,在板正面形成"O"形裂隙的同时反面形成"X"形裂隙,正面形成"U"形裂隙的同时反面形成"Y"形裂隙;最后,正反面裂缝贯通形成"横O-X"型初次破断和"横U-Y"型周期破断,在工作面上方形成"弧形三角板"和巷道上方形成"梯形板"的破断块体结构。统计发现,"横O-X"型初次破断步距与"横U-Y"型周期破断步距长度基本一致;横向破断形成的"弧形三角板"块体角度为75°~78°,与腰线和弧形切线形成的夹角72°~82°基本相等,近似于一个等角的"弧形三角板"。砌块模型试验结果表明,"弧形三角板"块体大幅回转过程中,因其顶点易与"梯形板"结构发生回转变形失稳而出现脱离现象,导致"弧形三角板"滑落失稳从而会引发工作面强矿压。研究成果为大采高开采工作面强矿压灾害防治提供试验基础。

In response to the mining of the water-carrying fracture zone in some hard roof mines and the horizontal"O-X"breakage and movement in the high-level key strata at the height of 8 to 15 times the mining height above the stope in the mining-induced water flowing fracture zone,which caused some dynamic disasters such as dynamic weighting and support crushing in the stope,floor heave happening 100 m to 200 m ahead of working face in the roadway adjacent to gob. The self-made large-scale three-dimensional physical simulation experiment platform was used to study the characteristics of breakage and movement of high-level key strata. The results show that when the key layer is broken horizontally,the long sides of the front side of the key layer and the middle axis direction of the reverse side form a crack at the same time. Then,the curved fracture formed in the two short sides on the front surface simultaneously,and separated fractures from a junction formed in the end point of middle fracture on the reverse surface. An"O"-shaped crack is formed on the front side of the plate and an"X"-shaped crack is formed on the reverse side,while a"U"-shaped crack is formed on the front side and a"Y"-shaped crack is formed on the reverse side. Finally,the positive and reverse cracks penetrate through to form a "transverse O-X"type initial break and a"transverse U-Y"type periodic break,forming a"curved triangular plate"above the working face and a "trapezoid plate"broken block structure above the roadway. The statistical results showed that the initial breakage interval of"horizontal O-X"was nearly the same as the periodical breakage intervals of"horizontal U-Y". Generally,the value of the vertex angle of the curved triangle plate was between 75°and 78°,which was almost equal to the angle between the waist line and arc line as the value was between 72° and 82°.Therefore,the curved triangle plate could be roughly regarded as a "curved equiangular triangle plate". The experimental results of the block model show that the curved triangle plate easily slid to instability and caused strong ground pressure behavior in the stope due to the rotation and instability of the"trapezoidal plate"structure,resulting in the detachment phenomenon. The research findings can provide an experimental reference for the prevention and control of strong mining pressure disasters in working faces with large mining height.