煤矿井底煤仓内散体颗粒三维结构分析

Three dimensional structure analysis of granular particles in the shaft coal pocket

煤矿中井底煤仓装卸煤过程实际上为仓内散体物料对仓壁力学作用过程,其侧压力出现原因一直是研究的难点,确定合理的仓壁径向压力是研究的关键。以直立筒状井底煤仓为例,通过简化井底煤仓建立了仓内贮料卸载过程中散体颗粒形成的三维立体承载结构力学模型,从散体力学角度进行了理论分析,并结合PFC^(3D)数值模拟实验及三维物理相似模拟实验模拟了井底煤仓卸料过程。结果表明:仓壁承受的侧压力主要是仓内煤矸散体颗粒在流动过程中相互挤压形成类似“三维锥壳”承载结构引起的。随着井底煤仓卸煤,仓内散体贮料不断放出,该结构不断形成和失稳,导致“三维锥壳”结构的支承点作用于仓壁形成动载,并随时间推移呈现卸载超压现象。散体颗粒对仓壁作用力与内部所形成的承载结构及上部荷载有关,结构稳定性受仓内散体贮料颗粒的粒径影响最大,内摩擦角及黏聚力次之,与现场工程实际及三维物理模拟实验具有较好的一致性。

Loading or unloading coal in the shaft coal pocket of the mine is a mechanical action of the bulk material to the wall of the bunker,the causes of lateral pressure is always under discussion,and it is the key to determine a reasonable radial force of the silo wall.Taking the vertical shaft coal pocket as an example,by simplifying the mechanical model of the shaft coal pocket,the mechanical model of the solid parabolic bearing structure formed by the granular particles in the process of unloading is established,and the analysis of the unloading process of the bunker is made combining with the PFC^(3D) numerical simulation experiment and three-dimensional physical similarity simulation experiment.The results show that:the main reason for the mechanical behavior of the silo wall is that the bulk coal and gangue particles squeeze each other to form a“three dimensional conical shell”bearing structure during the flow process.In the coal unloading process,the structure constantly forms and loses stability,and finally leads to the change of the force acting on the wall at the lower arch angle,resulting in unloading overpressure.According to the theory of bulk mechanics,the bearing characteristics of the structure are analyzed,and the expression of the force of the silo wall on the structure is derived.It is found that the effect of granular particles on the wall is related to the internal bearing structure and the upper load.The stability of the structure is mainly affected by the particle size of the bulk material stored in the silo,followed by the internal friction angle and cohesion,which is consistent with the field engineering practice and three-dimensional physical simulation experiment.