矸石浆体输送阻力特性及采空区流动规律试验研究

Experimental research on transport-resistance characteristics of gangue slurry and its flow trend in goaf

浆体充填是一种低干扰条件下矸石无害化处置的重要技术手段,保证浆体在管道中安全输送及在采空区中稳定流动是充填系统稳定运行的基础。为深入研究矸石及矸石浆体基本特性、浆体输送阻力特性及采空区流动规律,通过X射线衍射试验、电镜扫描试验、矸石粒径分布试验、浆体塌落度试验得到了矸石及矸石浆体的基本特性参数;设计了矸石浆体长距离环管输送试验系统,并针对不同流速进行环管试验,建立浆体流速与沿程阻力的关系,确定最佳工作流速及该条件下的沿程阻力;开展邻位注浆充填采空区流动扩散试验,掌握浆体在采空区垮落带内的流动扩散规律,测定试验条件下浆体在采空区内的自流坡度,揭示浆体流动过程颗粒沉降规律;并对矸石浆体邻位注浆充填进行了工程应用。研究结果表明:矸石的物相组成包括主要包括石英、高岭石,有部分长石、云母和少量的绿泥石、方解石、菱铁矿、黄铁矿等矿物,粒径分布为1250~3000μm(18.18%),630~1250μm(18.99%),315~630μm(19.35%),160~315μm(15.02%),75~160μm(11.73%),<75μm(16.74%),70%质量分数的矸石浆体塌落度为28.1 cm,扩展度为50.1 cm,自流坡度为3.8%,具有较好的流动性;浆体管道输送的沿程阻力随流速的增加而增加,且近似成正比关系,拟合关系函数为y=0.60244 x+0.78411,确定试验浆体在管径为ø60 mm条件下最佳工作流速为1.50 m/s,其沿程阻力为1.68 kPa/m;浆体采空区内流动规律整体呈现先纵向扩展再横向扩散的规律,首先在出料口下方形成半圆形覆盖层,然后继续向底部扩展形成纵向扩展通道,待浆体沿纵向通道扩散至底部边界时,浆体开始沿横向扩散,稳定后浆体平均自流坡度为7.1%,且固体颗粒在采空区流动过程中出现颗粒分选现象,在浆体流动方向上<74μm细颗粒比例有所升高,>74μm的粗颗粒比例有所下降。工程应用结果表明,充填期间矸石浆体管道输送状态稳定,浆体中的固体颗粒未发生淤积,且浆体在采空区空隙空间流动性极佳,未出现聚集沉降现象,根据钻孔窥视结果,浆体扩散距离大于45 m,设计的浆体管道输送流速、浆体级配质量分数合理,满足系统要求。

Slurry filling is deemed as a significant technique for harmless disposal of gangue under the condition of low interference.The safe transport of slurry in the pipe and its stable flow in the goaf area lays the foundation for the reliable operation of filling system.In order to deeply study the fundamental characteristics of gangue and slurry,and the piping resistance and flow dynamics of slurry in the goaf area,the basic parameters of gangue and gangue slurry were obtained through X-ray diffraction test,electron microscope scanning test,gangue particle size distribution test as well as slurry slump test.A long-distance loop piping system for transporting gangue slurry was designed and a series of loop piping tests were carried out under different flow velocities,thus the relationship between transport velocity and friction loss was established and the optimized transport velocity and friction loss of slurry could be determined.Then,grouting tests were carried out in the adjacent goaf to analyze the flow and diffusion characteristics of slurry within the caving zone of the goaf area and measure the slurry flow induced by gravity gradient in the goaf,thereby revealing the particle sedimentation law in the process of slurry flow.According to the testing results,the engineering application of gangue slurry in grouting filling in the adjacent goaf was provided.The research shows that the gangue is predominantly composed of quartz and kaolinite.Also,some feldspar and mica,and a small amount of chlorite,calcite,siderite,pyrite,and other minerals could be found in the gangue.The particle size ranging from 1250μm to 3000μm,from 630μm to 1250μm,from 315μm to 630μm,from 160μm to 315μm,from 75μm to 160μm as well as particle size smaller than 75μm account for 18.18%,18.99%,19.35%,15.02%,11.73%,and 16.74%respectively.In addition,70%of slurry containing gangue has a slump of 28.1 cm,a slump flow of 50.1 cm as well as the flowing slope induced by gravity of 3.85,which demonstrating a decent flowability.The resistance along with the slurry pipeline increases with flow velocity and an approximately proportional relationship could be found and expressed as y=0.60244x+0.78411.When the diameter of the pipeline is 60 mm,the optimal transport velocity and friction loss are determined to be 1.50 m/s and 1.68 kPa/m.Overall,the slurry flowing characteristics presents trends of first vertically expanding and then horizontally diffusing.A semi-circular covering layer is firstly formed under the discharging port,and then the slurry travels across the covering layer and spreads towards the bottom floor.Once it reaches the bottom boundary,it starts to diffuse laterally,with the average flowing slope induced by gravity reaching 7.1%after stabilization.In addition,particle separation phenomena could be observed when the solid particles flow in the goaf area,with the proportion of fine particles smaller than 200 mesh increasing slightly and coarse particles bigger than 200 mesh reducing in the flowing direction of slurry.The engineering application indicates that the gangue slurry could be reliably piped without sedimentation amid filling,and no aggregation and settlement occur within the permeable space of goaf,meaning that the slurry shows an excellent flowability.According to the visual results through the peepholes,the spreading distance of slurry could exceed 45 m,which means that the slurry piping velocity and gradient concentration have been reasonably designed to meet the system requirements.