浅埋采场上覆岩层孔隙率的时空分布特征

流场分布不均常造成采场上覆岩层瓦斯易富集、抽采区域难划分及采空区后方火灾难治理等问题，而上覆岩层在垮落期间的孔隙率分布特征是导致流场分布不均的主要因素之一。根据内蒙古某矿的浅埋煤层的地质资料，利用PFC2D(Particle Flow Code)的黏结颗粒模型(Bonded Particle Model,BPM)，借助弹性模量(90组试验)、泊松比(90组试验)、抗压强度(80组试验)及抗拉强度(80组试验)与岩体细观参数之间的关系，建立浅埋煤层模型。对其初次来压期间的上覆岩层的破坏过程、破坏形态、及破坏范围进行了研究，记录并分析采场动态推进过程中，顶底板岩层垂直应力的动态演化特征及孔隙率演化规律。结果表明：利用PFC软件能够很好的模拟上覆岩层垮落过程，其结果与已应用成熟的FLAC模拟相符合。

Space-time porosity distribution on overlying strata above a shallow seam

Flow field maldistribution often leads to problems,such as the easy enrichment of stope overburden gas,the division difficulty of extraction area,and the problem of rear gob fire difficult governance.And the overburden porosity distribution during caving is one of the main factors causing the flow field maldistribution.The model of long wall top-coal caving is established with the relationship between elastic modulus,Poisson ratio,compressive strength,and tensile strength with microscopic parameters of rock,which is on the basis of the geological column of one mine in Inner Mongolia and using the Bonded Particle Model (BPM) in Particle Flow Code (PFC2D).Analyzing the failure process,the failure mode and the failure range of excavating overburden strata,the vertical stress evolutionary process of rock mass in coal seam roof and floor and the evolution laws of porosity are recorded during the course of the stope moving.The results show that using PFC software simulates overburden strata failure process well,and the result corresponds to that simulated by FLAC.