Feasibility Study on In-Situ Driving Roadway along Goaf in Three Soft Thick Coal Seam

Abstract

Uniaxial compression, triaxial compression and coal crushing experiment were tested to get the soft the three soft characteristics of coal seam and surrounding rock in the third teaching mine in western Henan. Considering the influence of water and argillaceous composition, the relationship between the waste rock expansion factor and pressure was obtained after correction. Introducing the relationship into the calculation of maximum lateral bearing pressure point and collapse characteristic distribution, its results were in good agreement with the measured and simulated results. Establishing the accumulation form factor, “v”, of gob waste rocks in trend, and the representation of “v” was obtained by theoretical calculation. After a lot of calculations to analysis the relationship of “v” and “N”, “q 1”, “Kp ”, “H”, “m”, “Rt ”, and a lot of numerical simulations by 3dec, the results were got below: When the thickness of the direct roof was large, 1<“v”,the lower park of direct roof was collapsed and accumulate naturally, and the upper park was formed an arch bearing structure. While, the roadway excavation in this situation was larger than the condition of “v”<1 in the early stage, but its excavation was easy with broken wall rock, and the roadway deformation and maintenance were smaller with the protection by the arch bearing structure. The more soft the coal seam, its deformation toward gob and the distance between maximum lateral bearing pressure point and coal wall were more larger, and driving along the goaf would recover a large amount of coal. Under truss support,roadway deformation decreased significantly and very similar to the experimented results in situ. So when the seam and direct roof was soft, thick, and 1<“v”, driving roadway along goaf in situ was in the low stress zone protected by the arch bearing structure formed above, and it was a good engineering conditions for the recovery of coal in the gob, and for the overall roadway excavation with one-time laying of the anchor rod and metal mesh. This was the reason why roadway excavation along the goaf was mainly used for mining medium thick or thick coal seams with gentle inclination, inclination and large thickness.