千米深井大采高工作面超前切顶卸压软岩大巷防护技术

    The protection technology of advanced roof cutting and pressure relief soft rock roadway in large mining height working face in kilometer-deep mine

    • 摘要: 千米深井大巷受“三高一扰动”影响,围岩控制困难,其中,厚煤层采动影响下软岩大巷变形破坏问题尤为突出,影响工作面安全回采。本文以口孜东煤矿14采区为工程背景,得到140502工作面回采末期软岩大巷变形破坏规律,进行大巷变形破坏原因力学分析,提出围岩破坏能量判据,得出悬臂长度L3越长,大巷围岩内能量U越大,获得大巷严重变形破坏原因,即大巷围岩长期承受高静应力作用,对于动载扰动作用影响更为敏感,极易变形破碎。进一步建立工作面悬臂楔形结构力学模型,发现悬臂角度与超前支承应力的峰值呈现负相关,即悬臂角度愈大,超前支承应力的峰值愈小。据此提出停采线超前爆破切顶卸压巷道控制技术,通过理论分析设计了钻孔角度、高度、位置等切顶卸压参数,利用FLAC3D比选切顶范围,降低了爆破施工量。最后,制定140504工作面爆破切顶卸压方案,即在140504工作面风巷内停采线外17 m、23 m处分别布置一组相同的爆破面,超前工作面回采150 m起爆,每组断面斜向上穿层设计5个钻孔,呈扇形分布,布置钻孔时应避开工作面顶板上方存在的140504工作面高抽巷。在工作面回采期间对三条大巷展开监测,结果表明,140504工作面回采后西翼回风大巷、西翼主运胶带机大巷及西翼轨道大巷两帮移近量分别为17.6 cm、13.4 cm和8.4 cm。相较于140502工作面回采期间两帮移近量分别减小64.08%、60.59%和30.00%,控制效果较好,保障了工作面安全回采。

       

      Abstract: In deep mines with kilometer-level shafts, the surrounding rock control is challenging due to the combined effects of “three-high conditions and dynamic disturbances”(high stress, high temperature, and high permeability pressure, coupled with mining-induced disturbances). Among these issues, the deformation and failure of soft rock roadways under thick coal seam mining activities are particularly severe, threatening the safe extraction of working faces. Taking the 14th Mining Area of Kouzidong Coal Mine as the engineering background, this paper investigates the deformation and failure patterns of soft rock roadways during the final stage of mining at Face 140502. A mechanical analysis of roadway failure mechanisms is conducted, leading to the establishment of an energy-based failure criterion for surrounding rock. It is found that as the cantilever length L3 increases, the energy U stored in the roadway’s surrounding rock also increases. The severe deformation and failure of roadways are attributed to the long-term high static stress acting on the surrounding rock, which becomes highly sensitive to dynamic disturbances, resulting in rapid fracturing and instability. Additionally, a mechanical model of the cantilever wedge-shaped structure at the working face is developed. The analysis reveals a negative correlation between the cantilever angle and the peak value of the advanced abutment stress, i.e., a larger cantilever angle corresponds to a lower peak stress. Based on these findings, a roadway control technology involving advanced blasting and roof cutting pressure relief at the stopping line is proposed. Theoretical analysis guides the design of key parameters such as drilling angles, heights, and positions for pressure relief. FLAC3D simulations are utilized to optimize the roof cutting range, thereby reducing the required blasting workload. Finally, a blasting and roof cutting pressure relief scheme is implemented for Face 140504. Specifically, two identical blasting surfaces are positioned 17 m and 23 m outside the stopping line in the ventilation roadway of Face 140504. These blasts are initiated 150 m ahead of the mining face. Each section included five upward-inclined boreholes arranges in a fan-shaped pattern, carefully avoiding the existing high-level gas drainage roadway above the roof of Face 140504. During mining, monitoring of three major roadways shows that the sidewall convergence of the West Wing Return Airway, West Wing Main Conveyor Belt Roadway, and West Wing Track Roadway after Face 140504 extraction is 17.6 cm, 13.4 cm, and 8.4 cm, respectively. Compared to the convergence observed during Face 140502 mining, these values decrease by 64.08%, 60.59%, and 30%, demonstrating effective control and ensuring safe coal extraction.

       

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