基于断裂力学的特厚煤层综放开采顶板破断规律研究

针对特厚煤层综放开采过程中矿压显现剧烈支架工作阻力难以确定的问题，结合特厚煤层工作面顶板岩层破断形成的悬臂梁-砌体梁力学结构模型。工作面来压阶段支架工作阻力不足时，引起砌体梁结构下沉使悬臂梁结构回转变形破断，造成上覆砌体梁结构滑落失稳压架使工作面矿压显现剧烈的特点，建立了含中心斜裂纹的悬臂梁结构破断的力学模型，应用断裂力学理论，分析了悬臂梁破断失稳的影响因素，推导了支架荷载的表达式。结果表明：裂纹倾角和长度是悬臂梁破断失稳的主要影响因素；支架荷载除与悬臂梁自身因素有关外，还与砌体梁垮落步距等因素相关。结合塔山煤矿8102综采工作面地质条件，计算了支架荷载的理论值，验证了理论分析的合理性。理论研究成果对于分析特厚煤层开采时的支架荷载的大小，合理选择支架减少顶板事故具有一定的工程实际意义。

Study of roof breaking law of fully mechanized top coal caving mining in ultra-thick coal seam based on fracture mechanics

To solve the problems of the sharply appeared mine pressure and determination of the support working resistance in mechanized caving mining process of the ultra-thick coal seam, a structural model of cantilever beam-masonry beam is considered. When the support resistance is low at the time of face pressing, the subsidence of masonry beam results in the rotational deformation and the failure of cantilever beam. Furthermore, it leads to the slide breaking and pressing frame of the cantilever beam and the violent behavior of mine pressure. A mechanical model of breaking cantilever beam structure with a central crack is thus established. The effect of a serious of factors on the failure of the cantilever beam is analyzed by using fracture mechanics theory, and the expression of the support load is derived. The results show that the angle and length of the crack are the main factors influencing the failure of the cantilever beam. In addition, the support load is also relevant to other factors such as the falling step distance of the masonry beam. Based on the geological conditions of the fully mechanized working face 8102 in Tashan mine, the calculated support loads are used to verify the theoretical analysis. The results are of practical significance for analyzing the support load of ultra-thick coal seam mining and for providing reasonable selection of support to reduce the roof accident.