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在易碎顶板条件下,梁端至煤壁间的无支护区由于水平拉应力的存在极易冒落,给顶板控制造成了一定困难。通过正交分级因素设计,运用有限元法分析了9个因素(直接顶、底板、老顶、煤层的杨氏模量,直接顶厚度与采高之比,端面距,支架柱腿倾角,支架工作阻力,煤层埋深)对无支护区拉应力大小的影响。结果表明:底板条件和煤层埋深影响最小。所得回归公式能确定出无支护区的最大水平应力值,该公式是所保留的7个因素的函数。列举两例说明了公式的应用情况。
Under the condition of fragile roof, unsupported area between the beam end and the coal wall is easy to fall due to the horizontal tensile stress, which causes certain difficulties to roof control. Through the orthogonal grading factor design, nine factors (direct top, bottom plate, old top, the Young’s modulus of the coal seam, the ratio between the direct top thickness and the height of mining, the distance between the end face and the leg of the support leg, Working resistance, coal seam depth) on the tensile stress of unsupported area. The results show that the floor conditions and the depth of the coal seam have the least effect. The resulting regression formula determines the maximum horizontal stress in the zone without support, which is a function of the seven remaining factors. Two examples are given to illustrate the application of the formula.