The ore-body in - 95 m sublevel 4* slope of Beiminghe Iron Mine is gently inclined medium thick ore-body,and the floor of ore-body is at unstable strata and the fissure grows in joint. Moreover,it has been bearing the mining pressure from adjacent slopes for two years. The side fall root caving appeared during the tunneling of cross roadway and slope or after tunneling. Although lots of compressible "U"-shaped metal arch are adopted in secondary support, but the drifts'deformation and destruction canl be controlled. Therefore,the pressure relief measures are used, obtaining remarkable effect The paper described the depressurized mining experience of 4 slope in detail,and discussed the parameters and the best lime of pressure relief.%北洺河铁矿-95 m水平4#采场为缓倾斜中厚矿体,矿体底板含不稳岩层,岩体节理裂隙发育,而且受相邻采场采动压力作用的时间长达2a之久,进路联巷及回采进路在掘进过程中或成巷后不久就发生片帮冒顶.二次支护中投人大量U型可缩式金属拱架,但仍未能控制住巷道围岩的变形与破坏.为此采用了卸压措施,获得显著成效.详细介绍了4#采场的卸压开采经验,并对卸压参数与最佳卸压时间等进行讨论.
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