切顶卸压无煤柱自成巷开采与常规开采应力场分布特征对比分析

为了探索切顶卸压无煤柱自成巷开采与常规留煤柱开采应力分布的区别,以国内外首个切顶卸压无煤柱自成巷开采工业性试验为工程背景,运用FLAC3D数值模拟软件建立了大煤柱开采,小煤柱开采Ⅰ(相邻工作面回采巷道未掘),小煤柱开采Ⅱ(相邻工作面回采巷道已掘),无煤柱开采4种不同开采方式的数值计算模型,并对其应力分布特征进行了模拟和对比分析。得出如下规律:在工作面前方,平行于工作面长度方向,煤柱留设方式对应力分布的影响存在一定范围,在影响范围内垂直应力大小关系为:小煤柱开采Ⅱ大煤柱开采小煤柱开采Ⅰ无煤柱开采;留大煤柱,小煤柱开采时,靠近本工作面回采巷道附近均存在明显的应力集中,而无煤柱自成巷开采由于取消了超前掘进巷道,从而消除了掘巷引起的应力集中;在工作面侧向,大煤柱开采应力集中位置始终位于大煤柱内部,小煤柱开采Ⅱ位于下区段工作面实体煤内部,小煤柱开采Ⅰ和无煤柱开采则位于巷道煤帮内部,应力峰值位置与巷道距离大小关系为:无煤柱开采小煤柱开采Ⅰ小煤柱开采Ⅱ和大煤柱开采;大煤柱开采时侧向应力峰值最大,小煤柱开采时次之,无煤柱开采最小,其峰值较大煤柱开采降低18.1%~20.3%,较小煤柱开采Ⅱ降低11.8%~17.3%,采空区顶板稳定后,无煤柱开采和小煤柱开采Ⅰ峰值较为接近。

Comparative analysis on stress field distributions in roof cutting non-pillar mining method and conventional mining method

To explore the difference of stress field distributions in roof cutting non-pillar mining method and conventional pillar mining method,four numerical models,i.e.large coal pillar mining pattern (LCP),small coal pillar mining pattern with adjacent gateroad unexcavated (SCP Ⅰ),small coal pillar mining pattern with adjacent gateroad excavated (SCP Ⅱ) and non-coal pillar mining pattern (NCP),have been built based on the first industrial test of NCP by roof cutting and pressure release.The difference of the stress field distributions in those four types of mining patterns are studied and analyzed.The results show that in front of the mining face,the influence of pillars has a limited range,where the vertical stress in these four mining patterns decreased orderly with the sequence of SCP Ⅱ,LCP,SCP Ⅰ and NCP.In the mining pattern of LCP,SCP Ⅰ and SCP Ⅱ,the abutment stress is highly concentrated around the gateroad.However,there is no stress concentration in NCP because the gateroad is canceled in this new mining pattern.At the side of mining face,the stress-concentrated position is in the large coal pillar in the LCP mining pattern,whereas the stress-concentrated position is in the integrated coal of next mining panel in the SCP Ⅱ mining pattern.The stress-concentrated positions of SCP Ⅰ and NCP are in the internal coal rib.As the pillar size decreases,the position of the peak stress becomes farther to the gateroad rib.The peak stress in LCP is the largest while that of NCP is the minimum.In terms of the peak stress,the peak value in NCP decreases by 18.1%-20.3% compared with that in LCP and 11.8%-17.3% compared with that in SCP Ⅱ.Moreover,when the roof is stabilized,the peak stresses in NCP and SCP Ⅰ are similar.