North China coalfield is one of the most severe coal fields threatened by Ordovician limestone water (buried depth exceeding 1000 m). In this paper, the hydraulic mechanism of Ordovician limestone water in the complex geological structure are studied. An interesting phenomenon was found in the study, the water inrush from Ordovician limestone has a “latent period” and presents lag water inrush law. The hydrochemical characteristics of the early stage in Xingdong coal mine is non-Ordovician limestone water chemical characteristics, the later stage gradually shows the Ordovician limestone water with the continuous outflow. Meanwhile, the hyperbolic contour distribution characteristics are also observed in the spatial distribution law of microseismic in the floor working face. The minimum damage area is in the layer at the hyperbolic apex, which is the critical breakthrough point of water inrush. Furthermore, the water inrush fracture mechanics model (WIFM) of concealed fault with high confined water is established based on the fracture mechanics theory. The results show that the critical values of the length and angle of the water inrush of the conceal fault are about 50 m and 40°. It should be pointed out that the longer and larger angle conceal faults indicate the longer of the fracture expansion at the tip of the fault, and the probability of water inrush increases. Special attention should be paid to such concealed faults and methods such as grouting should be adopted to avoid the water inrush disaster caused by the activation of faults. This model provides a theoretical basis for the mechanical mechanism of the coal seam floor water inrush process.

中文翻译：

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基于断裂力学和微震监测的突水断裂力学模型研究

华北煤田是受奥陶系石灰岩水（埋深超过1000 m）威胁最严重的煤田之一。本文对复杂地质构造中奥陶系灰岩水的水力机理进行了研究。研究中发现一个有趣的现象，奥陶系灰岩突水存在一个“潜伏期”，呈现滞后突水规律。兴东煤矿前期水化学特征为非奥陶系石灰岩水化学特征，后期随着不断外流逐渐呈现奥陶系石灰岩水化学特征。同时，底板工作面微震空间分布规律也呈现出双曲线等值线分布特征。损伤最小区域为双曲顶点层，是突水的关键突破点。进一步，基于断裂力学理论，建立了高承压水隐伏断层突水断裂力学模型（WIFM）。结果表明，隐伏断层突水长度和角度的临界值约为50 m和40°。需要指出的是，隐伏断层越长、角度越大，表明断层尖端裂缝扩展时间越长，突水概率增大。对于此类隐蔽断层应特别关注，采取注浆等方法，避免断层激活引发突水灾害。该模型为煤层底板突水过程的力学机理提供了理论依据。