大采高复合型煤壁非同步片帮机理研究

Composite rib with large mining height is an objective existence during the actual mining, and the initial location, trace shape and seam order of the spalling are different from the homogeneous rib. This project divide composite rib into weak layer and (main) bearing layers. The nonsynchronous spalling process of composite rib is simulated through similar material test. First, based on the sound wave and coordinate measurement, the lateral damage dilatation features are obtained, and then the induced mechanism of nonsynchronous spalling is analyzed. Second, using digital speckle and stress-strain measurement, horizontal gradient distribution of surface strain field and internal stress field in main bearing layer is obtained, and the time-space relationship between brittle fracture of main bearing layer and stress-strain evolution is explored deeply. Finally, according to vertical gradient evolution process of the stress field and strain field in composite rib, a theory of layering weakening is proposed, and then the mechanical behavior and weakening duration of the weak layer and main bearing layers are obtained. Differential control mechanism is taken shape at the same time. The research results include the induced mechanism, key mechanism, spalling essence and differential control of nonsynchronous spalling about composite rib which will provide key theoretical and technical support for the scientific control of composite rib.

大采高复合型煤壁是回采一线经常性接触客观实体，其片帮初始位置、迹线形状、层位次序等基本特征不同于大采高均质煤壁，表现出典型的非同步片帮现象。本项目将复合型煤壁分为软弱分层和(主)承载分层，通过相似材料试验模拟大采高复合型煤壁非同步片帮发生过程：首先，基于声波测速和全站仪坐标测量，得出软弱分层横向损伤扩容特征，明晰复合型煤壁非同步片帮诱发机制；其次，采用数字散斑和应变测试方法，获得主承载分层表层应变场和内部应力场水平梯度分布，深究主承载分层脆性破断与其表层应变和内部应力演化之间的时空关系；最后，根据大采高复合型煤壁应变场和应力场垂直梯度演化过程，提出和凝练复合煤层强度分层弱化理论，得出软弱分层与主承载分层互馈力学行为和弱化时间关系，形成其差异调控机理。本项目研究成果集大采高复合型煤壁非同步片帮诱发机制、主导机制、片帮实质及差异调控于一体，为大采高复合型煤壁科学化调控提供了关键理论和技术支撑。

大采高复合型煤壁是回采一线经常性接触客观实体，其片帮初始位置、迹线形状、层位次序等基本特征不同于大采高均质煤壁，呈现典型的非同步片帮现象。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，研究表明：（1）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，软弱分层浅表煤壁纵向劈裂和深部煤壁损伤破裂显著降低了其支承性能，诱导复合煤壁整体片帮。（2）主承载分层给定载荷条件下悬臂梁式脆性破断是复合煤壁整体片帮的主控机制，复合煤壁整体片帮具有显著的识别特征：片帮断裂面深入煤壁距离较大且呈纵向贯通裂隙；主承载分层块状断裂体内无明显声发射迹象；软弱分层深部煤壁呈双剪切破坏模式，浅表煤壁出现粉碎性破坏，并伴随煤壁自由面块状剥落。（3）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，四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。本项目研究成果集大采高复合型煤壁非同步片帮诱发机制、主导机制、片帮实质及差异调控于一体，为大采高复合型煤壁科学化调控提供了关键理论和技术支撑。