浅埋超大采高工作面覆岩“切落体”结构模型及应用

针对浅埋煤层矿压显现强烈,易于发生切顶压架事故的问题,以神东矿区浅埋煤层为例,统计分析了7个矿、30余个综采工作面矿压数据,结果认为,与普通埋深及深部煤层相比,浅埋煤层工作面液压支架载荷大、周期来压步距短、动载系数大。采用钻孔位移计实测分析了上湾矿8.8 m超大采高工作面覆岩破断及地表岩移特征,破断位置位于工作面后上方,各层位测点呈整体同时破断,破断范围快速波及地表,当工作面推进11 m后,距顶板26 m处测点最大下沉量227 mm,当工作面推进296 m后,地表最大下沉量5.89 m。对比分析覆岩破断与液压支架工作阻力的对应关系,认为覆岩破断后没有直接与采空区矸石接触,而是形成某种结构并产生缓慢下沉现象。采用相似模拟方法分析了上湾矿8.8 m超大采高工作面覆岩破断及运动规律,认为正常情况下,呈整体同时破断的块体能够相互铰接并形成结构,当支护质量不足或者遇到地质异常区时,结构易发生整体滑落失稳,导致工作面压架事故。基于以上认识,提出了浅埋超大采高工作面覆岩"切落体"结构模型,分析了切落体结构的稳定条件及失稳类型,认为浅埋煤层覆岩呈整体切落式破断,形成以滑落失稳为主的铰接结构。研究得到了液压支架合理工作阻力计算公式,并以上湾8.8 m工作面为例进行了验算,结果表明,基于"切落体"结构计算的支架工作阻力能够满足工作面顶板支护要求。"切落体"结构为浅埋煤层液压支架合理工作阻力确定提供了理论依据,丰富了浅埋煤层开采岩层控制理论。

Cutting block structure model of overburden with shallow buried coal seam and ultra-large mining height working face

Based on the data of shallow buried workface measured at 30 working faces in seven collieries,the characteristics of ground pressure of workface were obtained,i.e.the intensive pressure phenomenon in workface is more serious than that in entries,the periodical pressure step is relatively shorter,the dynamic load coefficient is larger,the curve of hydraulic support resistance is monotonic rising and falling,the collapse of overburden strata extends to surface directly,the maximum subsidence of the distance to roof 26 m is 227 mm after the workface advancement 11 m,the maximum subsidence of surface is 5.89 m after the workface advancement 296 m,which is quite different from normal geotechnical condition that the ground pressure of workface is proportional to the depth of coal seams.Several observations and measurements about ground pressure were carried out in the super high 12401 mining workface with 8.8 m mining height in Shangwan colliery.A new model which described the broken structure of overburden in workface was proposed as a “cutting block” model which could explain the reasons why hydraulic supports were often pressured into end limited status in shallow buried geotechnical condition and obvious terraces were easily found on the surface where workface was below.In order to understand well for this new model,some physical simulations were built based on the 12401 workface practical strata in the experiment laboratory.A formula to calculate hydraulic powered supports working resistance was also derived from this model.The results were finally proved in Shangwan colliery.