Prediction of upper limit position of bedding separation overlying a coal roadway within an extra-thick coal seam

Abstract

Failure of the surrounding rock around a roadway induced by roof separation is one major type of underground roof-fall accidents. This failure can especially be commonly-seen in a bottom-driven roadway within an extra-thick coal seam (“bottom-driven roadway” is used throughout for ease of reference), containing weak partings in their roof coal seams. To determine the upper limit position of the roof interlayer separation is the primary premise for roof control. In this study, a mechanical model for predicting the interlayer separation overlying a bottom-driven roadway within an extra-thick coal seam was established and used to deduce the vertical stress, and length, of the elastic, and plastic zones in the rock strata above the wall of the roadway as well as the formulae for calculating the deflection in different regions of rock strata under bearing stress. Also, an approach was proposed, calculating the stratum load, deflection, and limiting span of the upper limit position of the interlayer separation in a thick coal seam. Based on the key strata control theory and its influence of bedding separation, a set of methods judging the upper limit position of the roof interlayer separation were constructed. In addition, the theoretical prediction and field monitoring for the upper limit position of interlayer separation were conducted in a typical roadway. The results obtained by these two methods are consistent, indicating that the methods proposed are conducive to improving roof control in a thick coal seam.

摘要

顶板离层致巷道围岩失稳破坏是煤矿井下冒顶灾变事故的主要类型之一, 其中以顶板煤层中含夹矸层的特厚煤层沿底巷道尤为突出, 而开展此类巷道顶板稳定性控制进而防止冒顶事故重要前提是合理确定顶板层间离层的上限位置。 本文以特厚煤层沿底巷道为研究对象, 针对顶板层间离层的上限位置合理确定问题, 综合运用力学计算、 理论分析、 现场监测等方法, 建立了特厚煤层巷道顶板层间离层数学模型, 理论推导得出了巷道顶板岩层侧向塑性区和弹性区的垂直应力、 长度及不同区域挠度方程式。 提出了一套判定特厚煤层巷道顶板层间离层上限位置的方法, 并结合数学力学计算方法推导得出层间离层上限位置确定所需要满足的荷载条件、 极限跨度、 挠度条件及顶板关键层位置与离层位置范围的判定式。 选择典型特厚煤层巷道进行层间离层上限值的理论分析和现场监测, 计算推导和数据监测结果显示两者确定的离层上限位置是一致的, 证明了提出的判定方法是正确的。