上覆高位岩浆岩下离层空间的演化规律及其预测

Evolution laws and prediction of separated stratum space under overlying high-position magmatic rocks

针对工作面上覆高位硬厚岩浆岩条件,采用相似材料模拟试验研究了主关键层下离层空间的演化过程与形态特征,分析了离层空间的层位演化与横向扩展规律、覆岩与主关键层的运移规律;通过理论分析揭示了离层空间形成的机理与条件,提出了离层空间演化特征的确定方法,建立了主关键层底部最大离层空间的分析模型与预测方法。研究表明:岩层组合失稳运移形成"月牙"形离层空间,以间歇式跳跃上升至岩浆岩底部,岩浆岩底部存在较大的离层空间,并由"月牙"形逐渐转变为"一字"形,岩浆岩破裂运移导致离层闭合。离层空间在亚关键层及主关键层底部自下而上动态发育与闭合,层位高度及发育范围与推进距离呈正相关性,可采用"多梯形"方法确定其演化过程。覆岩运移经历下位关键层沉降、运移向主关键层底部发展、底部盆地沉降、岩浆岩运移及整体稳定等5个状态,覆岩下沉形态先后呈"V"型、"√"型及"U"型。岩浆岩运移过程分为下部支撑、底部离层扩展、破裂随动、失稳运移及离层闭合稳定等5个阶段。建立了最大离层空间的覆岩结构及弹性基础梁模型,得到其断面积和体积的预测计算式,为高位岩浆岩下安全开采提供了理论依据。

According to the thick hard conditions of separated stratum space under overlying high-position magmatic rocks in working surface, the evolution rules and morphological characteristics of separated stratum space under the main key strata are studied by similar material simulation test. The horizon evolution and horizontal scaling law of separated stratum space and the migration law of overlying strata and the main key strata are analyzed. Through theoretical analysis, the formation mechanism and conditions of separated stratum space are revealed. A method to determine the evolution characteristics of separated strata space is put forward, and the analysis model and prediction method of the maximum separated stratum space at the bottom of main key strata are proposed. Researches show that the instability migration of combined strata forms a ＂crescent moon＂ shaped separated stratum space which intermittently jumps up to the bottom of the magmatic rocks. When the separated stratum space densely exists at the bottom of the magmatic rocks, and is gradually transformed from the ＂ crescent ＂ form into the ＂straight line ＂ one, the burst migration of magmatic rocks contributes to the closure of separated strata. The separated stratum space lies at the bottom of the inferior key stratum and the main key stratum dynamically developes and closes from bottom to top. There is a positive correlation between the layer heights together with the development scope and the advancing distance. The ＂multi-trapezium＂ method can be used to determine its evolution process. The migration of overlying strata experiences five-state subsidence of the inferior key stratum, development migration to the bottom of main key stratum, migration of the magmatic rocks and the overall stability. The subsidence form of the overlying strata is successively presented as shapes of ＂V＂, ＂√＂ and ＂U＂. The migration of magmatic rocks can also be divided into five steps which are named lower support, extension of the bottom separated stratum space, rupture of the follow-up, instability migration and stable closing of separated stratum space. The overlying strata structure of the maximum separated stratum space and the elastic foundation beam model are established, and the forecast formula for its area and volume is derived so as to provide theoretical basis for the safety mining under high magmatic rocks.