陕北侏罗纪煤田榆神矿区中鸡勘查区煤层厚度混合分布特征及其意义

Mixture distribution of coal seam thickness and its significance in Zhongji exploration zone of Yulin-Shenmu mining district in northern Shaanxi

煤层厚度统计分布及空间变化规律研究对煤矿勘探和生产建设具有重要作用。以陕北侏罗纪煤田榆神矿区中鸡勘查区详查工作中获取的83个钻孔数据为例,对三大主要可采煤层2-2煤、3-1煤、4-3煤的煤厚数据进行了探索性数据分析,认为3个层煤的煤厚数据均具有混合分布特征,进而采用MML-EM算法对煤层厚度数据进行了高斯有限混合总体筛分。由总体筛分结果可见2-2煤、3-1煤的煤厚数据近似服从由2个子分布组成的混合正态分布,4-3煤厚数据近似服从由3个子分布组成的混合正态分布。讨论了煤层底板高程与煤厚的相关关系,认为煤厚变化主要受底板高程变化影响。筛分所获取的低值与高值2个子正态分布可能分别对应于2种不同的沉积环境,即低值总体指示泥沙及砾石等沉积物的沉积速度大于植物遗体的沉积环境,高值总体则反之。

Statistical distribution and spatial variation seam thickness played an important role in coal exploration and coal mine construction. 83 boreholes data in Zhongji exploration zone, Yulin-Shenmu mining district, Jurassic coal field in northern Shaanxi were gathered. The exploratory data analysis （EDA） technique was used to analyze the coal seam thickness data from the three main mined seams No. 2-2, 3-1 , 4-3 and found they followed mixture distributions in the study area. The Gaussian infinite mixture populations were screened by MML-EM algorithm. The mixture distribution of thickness data of coal seam No. 2-5, 3-3 contained two subnormal distributions and data of coal seam No. 4-3 contained three subnormal distributions according to the screening results. The correlation between the elevation of the coal floor and coal thickness was discussed. The elevation of coal floor controlled the variation of coal thickness. The low-value and high-value subnormal distributions maybe corresponded to two kinds of sedimentary environments respectively. The low-value component indicated the speed of sand and gravel sediments was greater than that of plant debris, and the high-value component was vice versa.