Effects of increasing working faces length on underground pressure behaviors of mining super-high faces under shallow coal seam

By the industrial mining experiments and observed data of working faces No.51101 (240 m in length) and No.51104 (300 m in length) in Shangwan coal mine of Shenfu-Dongsheng mining district, the effects of increasing faces length on underground pressures behaviors were explored, and the conclusions are drawn as follows: (1) weighting span becomes shorter; (2) cycle weighting strength is relaxed; (3) the rock pressure distribution is shown that the quadric parabola relations can be used for the working faces middle point as symmetrical axis(i.e. coordinate origin); (4) the regression relation between maximum resistances and initial ones is liner; and (5) the supports loads in non-weighting period and underground pressure behavior with increasing faces length are enhanced, and roof weighting impact load was larger than the supports maximum resistance for large mining height and supper-long faces.