强冲击地压矿井煤层顶板覆岩结构研究——以孟村煤矿为例

Study on Roof Deposition Characteristics of Coal Seam in High Underground Pressure:A Case Study of the Mengcun Coal Mine

矿井工作面上覆坚硬厚层顶板对冲击地压的产生具有重要影响,顶板坚硬厚层砂岩通常因沉积相的变化在横向和纵向上呈现出厚度、顶底板起伏和岩石力学性质等方面的变化。陕西彬长矿区孟村煤矿地质条件复杂,主采煤层顶板发育多层厚砂岩,矿井长期受冲击地压灾害威胁。为准确掌握工作面顶板坚硬厚层砂体层位及展布状态等信息,对其进行压裂弱化,保障矿井安全高效开采,基于孟村煤矿工程地质条件,通过井下工作面巷道顶板钻孔取心编录和钻孔电视测井方法,进行工作面顶板覆岩结构探查,对顶板主要砂体采样,进行岩石学、沉积相和岩石物理力学性质等特征分析,得到如下主要成果:①孟村煤矿401103工作面顶板100m内可对比划分出5层连续的砂体,工作面沉积微相变化导致各砂体厚度和顶底板标高不稳定;②401103工作面顶板延安组二段、直罗组、安定组底部均为河流相沉积,河流微相中的天然堤相细粒砂岩和粉砂岩的岩石力学强度相对最大,随着岩石粒径的逐渐增大,边滩相和河床滞留相中、粗粒砂岩的强度相对降低。不同沉积环境同一粒级砂岩的岩石力学强度因石英含量增高、硅质胶结物含量增高、颗粒支撑结构等因素而增大;③井田现今构造应力和顶板坚硬厚层砂岩等是矿井冲击地压灾害的主要诱因,对上覆高位坚硬厚层砂体进行区域水力致裂弱化,可显著降低矿井冲击地压风险。

The hard thick roof on the coal mining face has an important influence on the generation of rock burst.The hard thick roof sandstone usually changes in thickness,roof and floor fluctuation and rock mechanical properties in the transverse and longitudinal aspects due to the change of sedimentary facies.The geological condition of Mengcun Coal mine in Binchang Mining area of Shaanxi province is complicated.The roof of the main coal seam is multi-layer thick sandstone,and the mine is threatened by rock burst disaster for a long time.In order to accurately grasp the position and distribution of the hard-and-thick sandstone of coal mining face,and carry out fracturing-weakening to ensure the safe and efficient mining,based on the engineering geological conditions of Mengcun coal mine,this study analyzed the characteristics of petrology,sedimentary facies and petrophysical and mechanical properties by exploring the roof overhanging structure of the coal mining face through the drilling and core-recording of the roadway roof and the drilling TV logging method,and samples the main sandstone bodies of the roof.The main results are as follow:①Five continuous layers of sandstone bodies can be correlated within 100m of the roof of 401103 coal mining face in Mengcun Coal Mine.The variation of sedimentary microfacies in coal mining face leads to the instability of the thickness and elevation of each sandstone body;②In the roof of 401103 coal mining face,the second section of Yan’an Formation,Zhiluo Formation and Anding Formation are all fluvial facies deposits.The rock mechanical strength of fine grained sandstone and siltstone of natural dike facies in fluvial microfacies is relatively the largest.With the gradual increase of rock particle size,the strength of coarse-grained sandstone in the bank facies and riverbed residual facies is relatively reduced.The rock mechanical strength of the same particle size sandstone in different sedimentary environments increases with the increase of quartz content,siliceous cement content and grain support structure.③The present tectonic stress of the mine field and the hard and thick sandstone in the roof are the main causes of mine rockburst disaster.The regional hydraulic-fracturing-weakening of the overlying hard and thick sandstone body can significantly reduce the risk of mine rockburst.