高位硬厚岩层破断规律及其动力响应分析

 以杨柳煤矿10416工作面高位硬厚岩浆岩条件为背景，建立高位硬厚岩层三边固支一边简支弹性薄板力学模型，利用瑞利–里兹法，推导出硬厚岩层挠曲函数与应力近似解析式，得到破断跨度的计算式，并根据覆岩破裂形态提出破断步距的计算方法。采用微震、支架压力及地表下沉等监测分析，揭示高位硬厚岩层破断失稳规律及其动力响应。研究表明：高位硬厚岩层破断前的挠度最大点为(x =a /2，y =13b/(10π)) (a为硬厚岩层走向悬露长度，b为硬厚岩层沿倾向的悬露长度)；当a＜1.049b时，硬厚岩层首先沿倾向固支边发生破断，否则首先沿走向固支边发生破断；硬厚岩层初次破断形式为沿走向对称而沿倾向非对称的“O-X”型，且破断后侧向跨度固支侧大于简支侧。高位硬厚岩层破断及运移过程中微震活动加剧，产生强微震活动，破断失稳期间支架压力显著升高，并引起地表下沉明显变化。高位硬厚岩层破断失稳引起强烈的动力响应，采用理论计算和微震监测可以进行分析预测。

FRACTURING AND DYNAMIC RESPONSE OF HIGH AND THICK STRATAS OF HARD ROCKS

An elastic model of thin plate with three edges fixed and one simply supported was established as the mechanical model of high and thick strata of hard magmatic rock at working front 10416 in Yangliu coal mine，A flexural function and an analytic expression of stresses for the hard and thick strata were derived with Rayleigh-Ritz method. A formula of fracture span was obtained；and then a method of calculating the length of drawing pace of fracturing according to fracture morphology of overburden was proposed. The analysis of monitored results of microseism，supporting pressures and surface subsidence revealed the fracture process and the dynamic response of high and thick strata of hard rocks. The point of maximum deflection prior to fracturing of strata is at the location of and ，where a is suspension length along the strike of hard-thick strata；b is suspension length along the tendency of hard-thick strata. Fracture first happened along the dip clamper edge if a＜1.049b，along the strike clamper edge otherwise. The initial form of fracturing is “O-X” shaped，which is symmetrically along the strike but asymmetrically along the tend. Microseismicity intensified during the process of fracturing and movement of strata leading to the strong microseismicities activities to be generated and the supporting pressure and surface subsidence significantly be increased. Fracturing of high and thick strata of hard rocks causes strong dynamic response which can be analyzed and predicted by theoretical calculation and microseismic monitoring.