Widely distributed in North China, Ordovician karst is characterized by having high thickness, nonuniform aquosity, and significant water pressure-bearing properties. Deep mining in North China is threatened by associated water hazards; hence, research on the hydrogeological characteristics of deep Ordovician karst is needed. In this study, the Weibei coalfield in Shaanxi Province, China, was selected as the study area, especially mines in the Hancheng and Chenghe mining areas. In situ experiments, including water pumping, water drainage, water injecting and water pressure, and laboratory experiments, were conducted to study the hydrogeological characteristics of the Ordovician karst top in the study area. A comprehensive analysis was conducted on controlling factors for the development of the Ordovician karst top in the study area, and a method for evaluating the water inrush risk in coal mining areas based on karst hydrogeological characteristics was proposed. The research results indicated that the Ordovician karst top in the study area was characterized by heterogeneity, vertical zonation, and partially filled properties, which were mainly controlled by two factors: sedimentation and tectonism. The hydrogeological conditions of the Ordovician karst could be divided into three types: nonfilled and nonsignificant tectonism, filled and nonsignificant tectonism, and significant tectonism. Among them, the filled and nonsignificant tectonism type Ordovician karst top type had a filling thickness of 20 m. Based on karst hydrogeological characteristics, the methods were proposed to evaluate the water inrush risk in the coal mining floor. The practical tests verified the methods.

中文翻译：

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深部奥陶系岩溶顶面水文特征及其对煤矿开采的威胁评价——以陕西渭北煤田为例

奥陶系岩溶在华北地区分布广泛，具有厚度大、含水量不均匀、承压性显着等特点。华北深部采矿受到相关水灾的威胁；因此，需要对奥陶系深部岩溶的水文地质特征进行研究。本次研究以陕西省渭北煤田为研究区，尤其是韩城矿区和城河矿区。通过抽水、排水、注水、水压等原位试验和室内试验，研究了研究区奥陶系岩溶顶面的水文地质特征。综合分析了研究区奥陶系岩溶顶发育的控制因素，提出了一种基于岩溶水文地质特征的煤矿区突水风险评价方法。研究结果表明，研究区奥陶系岩溶顶具有非均质性、垂直分带、部分充填等特征，主要受沉积作用和构造作用两大因素控制。奥陶系岩溶水文地质条件可分为不充填不显着构造作用、充填不显着构造作用和显着构造作用三种类型。其中，充填型和不显着构造型奥陶系岩溶顶型充填厚度为20 m。基于岩溶水文地质特征，提出了煤矿底板突水风险评价方法。实际测试验证了这些方法。