煤层开采后,上覆岩层发生破断运动,对巷道和回采工作面施加静载荷和动载荷,诱发煤层顶板和冲击矿压灾害。而上覆岩层的运动不仅是单个工作面回采的结果,也可能是多个工作面回采共同作用的结果。微震监测表明,对于采用小煤柱护巷,尤其是覆岩中存在厚层坚硬关键层的矿井,冲击矿压震源往往集中在相邻采空区中的厚硬岩层中,说明煤矿覆岩在空间上存在着结构,并且采空范围（边界条件）不同,覆岩的空间结构是动态演化的。空间结构演化与失稳过程中造成的冲击矿压动力灾害称为覆岩空间结构失稳型冲击矿压。为了揭示此类冲击矿压的机理,提出煤矿覆岩空间结构演化与诱冲机制,并采用实验室物理模拟试验、FLAC3D数值模拟试验、理论分析和工程实践4种方法进行研究。煤矿覆岩破断后的形态是空间结构,空间结构的形成与失稳是动态演化的。煤矿覆岩在层面方向上各关键层破断成＂O-X＂形态,不同层位的＂OX＂结构形态空间上形成柱台体,与之相邻的边界覆岩在竖向剖面上形成＂F＂型结构。覆岩层面方向破坏的＂OX＂结构向上发展,剖面方向上的＂F＂结构也会发生破断失稳。因此,＂OX＂与＂F＂结构及其相互转化构成了煤矿覆岩的整体空间结构形态,＂OX＂与＂F＂结构的形成与失稳不断进行,称为煤矿覆岩空间结构的动态演化循环。考虑顶板断裂线、煤柱稳定性与动态破坏3个因素,给出覆岩空间结构动态演化的条件判据,根据工作面受＂OX＂与＂F＂的影响程度不同,将工作面分为＂OX＂,＂F＂及＂T＂型空间结构工作面,并根据关键层的破断特征进行详细分类。通过实验室相似材料试验,模拟多工作面连续回采时＂OX＂,＂F＂,＂T＂型工作面的空间结构的形成与演化规律。FLAC3D模拟表明覆岩性质不变的情况下,采空区范围不同,煤层应力集中程度的规律为：短臂对称＂T＂〉非对称＂T＂〉短臂＂F＂〉长臂对称＂T＂〉长臂＂F＂〉＂OX＂,而关键层的来压次数则是长臂结构〉短臂结构。＂OX＂工作面应力集中随工作面宽度线性增大;短臂＂F＂工作面,长度增加有利于整个工作面范围内支承压力的降低;长臂＂F＂工作面,工作面加大,端头支承压力将降低,中部支承压力将升高;孤岛＂T＂工作面加大工作面宽度对工作面端头与中部的应力降低均有作用。基于弹性板与关键层理论,分析了＂OX＂结构破断与形成过程,给出了基于纳维解法的应力精确解,提出了＂F＂结构存在主动与被动两种失稳模式,被动失稳能导致下位结构呈整体滑落失稳,失稳速度快,厚度大,冲击力强,危险程度高于主动失稳过程。覆岩空间结构失稳型冲击矿压的本质为动静组合加载的复合型冲击。从应力、能量与震动效应构建了表示冲击发生的判据。动静组合加载的模拟表明,在动静载之和相等的情况下,高静载＋低动载的组合方式冲击危险性高于低静载＋高动载的组合。针对覆岩空间结构失稳型冲击矿压的特点,建立了以动静载应力场监测为基础,以空下巷道布置、定向高压水力致裂为关键技术的预防体系,通过济三煤矿＂F＂工作面63下05与＂T＂工作面163下02C的防冲实践验证了论文提出的覆岩空间演化诱冲机制能够有效地指导现场防冲工作。%The overlying strata fractures and moves as the result of coal seam exploitation,and in this process both stat- ic and dynamic load apply to the roadways and workfaces, inducing roof and rockhurst disaster. The movement of the o- verlying strata is not only the result of a single workface, but also the interaction of more workface. The traditional spa- tial structure of overlying strata in coal mine is usually plane model focused on the independent single workface, and few researches concern on the structural morphology and evolution mechanism that continuous exploitation of more workfaces. Microseismic monitoring results show that the rockburst sources are mainly concentrated in the adjacent gobs expecially when thick and hard key strata above the workfaces with small or none coal pillar between each other, which indicates spatial structure of overlying strata existed in the coal mine and the spatial structure evoluted dynami- cally with the boundary eontitions changes. The evolution and instability of the spatial structure induce various foms of strata behaviors, especially dynamic disasters of which roekbursts are most serious,was entitled spatial structure insta- bility roekburst. To reveal the mechanism of this new type rockburst, the spatial structure evolution model of overlying strata was putforward, and integrated approaches were adopted for deep research including laboratory physical simula- tion experiment, FLAC3D numerical simuliation, theoretical analysis and engineering practice.
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