厚层坚硬顶板变形能积聚与断裂能释放规律研究

High strength, highly integral and self-bearing ability are characteristics of hard roof.Large area suspends after the coal seam mining and does not easily fall down from worked out section in short term. First weighting and periodical weighting of stope are more intense and release large elastic deformation energy, which is easy to cause disaster accidents like rock burst. Therefore, the study of energy accumulation of hard roof in stope and energy release mechanism of fracture failure is very significant in coal seam mining safety under the condition of hard roof. Disaster mechanism of energy accumulation from hard roof deformation and energy release from fracture was targeted in this project research. Considering key and scientific problems like the bending deformation of hard roof, fracture and failure mechanism, mechanical model of energy accumulation from bend deformation of hard roof and energy release from fracture was established. By revealing influence law from load size ( intensity), strata stiffness, anti-bending stiffness of rock beam, hard roof thickness, the advancing speed, the length of stope mining and damage area of supporting coal on energy accumulation from hard roof in stope and release evolution, basic standard of stope surrounding rock control from hard roof was put forward. The studies in the project can be effective in predicting and controlling related dynamic calamity induced by hard roof movement and also provide theoretic basis and technical support for ensuring safety mining.

坚硬顶板强度高、整体性强、自承能力强，煤层开采后大面积悬露不易垮落，采场初次来压与周期来压均较强烈并释放大量弹性变形能，容易诱发冲击地压等灾害事故，因此研究采场坚硬顶板聚能与断裂破坏释放能量机理，对于坚硬顶板条件下煤层安全开采具有重要意义。本项目以坚硬顶板变形聚能与断裂能量释放诱灾机理为研究目标，围绕坚硬顶板的弯曲变形、断裂与破坏机理的关键科学问题，建立坚硬顶板弯曲变形蓄能与断裂释能的力学模型，揭示荷载大小（密集度）、地层刚度、岩梁抗弯刚度、顶板厚度、推进速度、采场长度、支承煤体破坏范围等对采场坚硬顶板能量聚集、释放演化的影响规律，提出坚硬顶板采场围岩控制的基本准则。本项目研究为科学预测与控制坚硬顶板运动诱发的相关动力灾害，保障开采安全提供理论依据与技术支持。

由于坚硬顶板强度高、厚度大、整体性强，煤层开采后，采场来压步距大，且来压突然、剧烈，经常发生顶板切断、冲击地压等煤矿灾害，不仅造成巨大的经济损失，而且严重威胁矿井安全生产。本课题针对煤矿采场厚层坚硬顶板变形能积聚与断裂能释放规律进行研究，运用理论分析、相似模拟试验、数值模拟及现场监测等方法，获得的主要研究成果有：（1）在覆岩均布力和增量压力共同作用且光滑连接的荷载作用下，将煤壁前方煤层和直接顶视为弹性地基，较工作面前方煤层-直接顶结构按刚性处理，更符合坚硬顶板受力实际，推导了初次来压和周期来压顶板断裂前、后煤壁前方的顶板挠度、弯矩及应变能密度分布关系式；（2）通过建立煤壁前方半无限弹性基础梁和采空区岩梁的挠曲线微分方程，以最大拉应变强度条件为裂纹发生条件，理论计算出了煤壁前方坚硬顶板的断裂位置，且煤质越硬，顶板裂缝与煤壁的距离越近；（3）坚硬顶板初次来压和周期来压期间，建立半无限弹性地基梁和采空区岩梁构成的超静定连续梁的挠曲线方程，求得按最大拉应力强度理论确定顶板超前断裂位置，从而分析了顶板断裂前后变形蓄能与断裂释能演化机理；（4）根据推导的坚硬顶板断裂前后顶板挠度、弯矩和弯曲应变能密度关系式，通过调整参数，可对不同采深、不同岩性和岩层结构的工作面煤壁前方的顶板挠度、弯矩和弯曲应变能密度关系进行计算；（5）采用相似材料模拟和现场监测方法，分析了工作面上覆坚硬顶板在采动过程中的运动规律，顶板初次来压运动的破坏形式为剪切破坏；坚硬顶板周期来压步距呈“小-大-小”交错运动的规律，且部分周期来压运动表现为剪断破坏；（6）运用数值模拟和现场监测方法，分析得到了工作面推进过程中坚硬顶板应变能“积聚-释放-积聚”的周期活动规律；应变能释放后，顶板岩层系统往安全方向发展。总之，本课题的研究成果揭示了坚硬顶板弯曲变形与断裂过程中能量演化规律，确定了初次断裂与周期断裂时坚硬顶板在煤壁前方的断裂位置，回答了坚硬顶板采场矿压控制难题，为坚硬顶板采场破断运动诱发灾害控制提供理论依据。