大采高复合煤壁非同步片帮分层弱化机制的试验研究

An experimental study of layered weakening mechanism to nonsynchronous spalling from composite rib with large mining height

建立几何相似比为1∶10的相似材料模型,研究大采高复合煤壁非同步片帮分层弱化机制.采用百分表和8通道声发射系统采集加载过程中复合煤壁不同分层的横向位移和破裂参量,对软弱分层和主承载分层的扩容特征和破裂特征进行试验观测和特性分析.结果表明:横向非同步扩容使得复合煤壁不同分层承载能力分化加剧,软弱分层超前损伤诱发复合煤壁非同步片帮;主承载分层给定载荷条件下悬臂梁脆性破断是复合煤壁整体片帮的主控机制;等值弱化、增强弱化、突变弱化和逆向弱化是复合煤壁非同步片帮分层弱化的主要演化模式,等值弱化是分层弱化的原始积累,增强弱化是分层弱化的主导趋势,突变弱化是分层弱化的质变起点,逆向弱化是分层弱化的短暂变异,4种弱化模式的时空组合直观阐释了复合煤壁非同步片帮力学行为的特异性.

A similar material model with similarity ratio 1∶10 was established to research the layered weakening mechanism to explain nonsynchronous spalling from composite rib with large mining height. A monitoring system comprised dial gauge and 8-channel acoustic emission(AE) system was used to collect data of lateral displacement and fracture parameters of different layers along with loading process. The dilatation and fracture behaviors of weak layer and main bearing layer were observed, then the characteristics and mechanisms were analyzed. The results show that the nonsynchronous lateral dilatation prompts the differentiation of bearing capability of different layers, and the speed-up damage of weak layer induces the nonsynchronous spalling of composite rib. Under a given loading, cantilever rupture of main bearing layer is identified to be the controlling mechanism of entire spalling. The main evolutionary model of nonsynchronous spalling contains equivalent weakening, enhanced weakening, mutation weakening and reverse weakening. The equivalent weakening, enhanced weakening and mutation weakening are primitive accumulation, dominant trend, qualitative change of layered weakening respectively, and the reverse weakening is a short variation of layered weakening. The space-time combination of four models explains the behavior specificity of nonsynchronous spalling of composite rib.