Study on effect of working face length on overburden caving form and force chain arch characteristics

Abstract

Using theoretical analysis combined with numerical simulation, the inclination composite force chain arch structure is proposed, and the characteristics of the force chain arch under the influence of surface length are analyzed. The research result shows that the inclination collapse rock formation presents in a “trapezoidal” collapse form that is gradually narrowed from bottom to top. When the length of the working face increases, the collapse height also increases. The strong chain is distributed in the form of flat arches or half arches, forming a composite force chain arch structure. The composite force chain-arch structure forms a carrier structure above the stope with coal pillars at two sides; the working face tends to be sparse with cracks in the middle, and the porosity is low, while dense cracks on both sides increase the porosity, the fracture field and porosity as a whole show the characteristics of “O” ring; the composite force chain arch structure transfers the overburden stress to the coal pillars on both sides, and when the length of the working face increases, the cracks of the coal pillars are more developed, and the stress concentrate coefficient increases.

Keywords

• working face inclination
• caving form
• effect of working face length
• force chain arch
• particle flow