神东矿区砂岩孔隙结构特征及与其物理力学性质的关系

摘要

In order to study the effect of pore structure on the mechanical properties of sandstone in Shendong mining area,the rock composition,microstructure and pore characteristics were obtained by polarizing micro-scope,scanning electron microscope,and nuclear magnetic resonance.Based on uniaxial compressive tests of sandstone with different types,the relationship between microstructure characteristics of sandstone and its uni- axial compressive strength,elastic modulus and poisson’s ratio was analyzed emphatically.The results showed that the main components of sandstone are quartz and feldspar,in which the content of quartz is above 15% , the content of feldspar is more than 40% ,and there is a small amount of mica.Siltstone is calcareous cementa-tion,fine grained sandstone and medium grained sandstone are argillaceous cementation;The pore diameter and particle diameter of sandstone basically obey normal distribution;The surface of siltstone is smooth and dense, with nebulous grain boundary,while small pores are distributed on the surface of fine-grained sandstone.The pore structure of middle grained sandstone is developed with cluster shape,and the degree of cementation is poor.The relationship between compressive strength and porosity of sandstone shows a negative exponential re-lationship.There is a critical point on the curves of compressive strength and porosity of sandstone,and the critical porosity increases with the increase of particle size and pore diameter;The elastic modulus of sandstone is negatively correlated with its porosity,in which the elastic modulus of siltstone and fine sandstone decreases exponentially,while the elastic modulus of the middle grained sandstone varies linearly; Poisson’s ratio of sandstone is not significantly associated with its porosity.%为了研究神东矿区砂岩的孔隙结构对其物理力学性质的影响,利用偏光显微镜、扫描电镜、核磁共振仪等仪器获得了砂岩成分、微观结构与孔隙特征,并进行不同类型砂岩单轴压缩试验,分析了砂岩的孔隙结构与其单轴抗压强度、弹性模量、泊松比之间的关系.结果表明:砂岩的主要成分为石英(15%以上)、长石(40%以上),并含有少量云母等;粉砂岩为钙质胶结,细粒和中粒砂岩为泥质胶结,砂岩的颗粒直径与孔隙大小基本服从正态分布;粉砂岩表面平整致密,颗粒边界模糊不清,细粒砂岩表面分布着细小的孔隙,中粒砂岩孔隙结构十分发育,颗粒呈团簇状,胶结程度较差;砂岩抗压强度与孔隙率之间呈负指数分布,抗压强度与孔隙率变化曲线存在临界点,随着颗粒、孔隙直径的增加,对应的临界孔隙率也在增大;砂岩弹性模量与孔隙率呈负相关,其中粉砂岩与细粒砂岩呈指数形式减少,中粒砂岩则呈线性减小;砂岩的泊松比与孔隙率无明显相关性.