曹家滩煤矿10 m超大采高工作面采场围岩控制技术

Surrounding rock control technology of 10 m super large mining height working face in Caojiatan Coal Mine

  • 摘要: 曹家滩煤矿10 m超大采高开采一次开采高度及开采强度为世界首创,采场围岩的有效控制为工作面能否安全高效开采的关键。在分析煤层赋存条件及已采工作面矿压显现特征的基础上,结合工作面超大开采空间、超高煤壁的特点,明确了10 m超大采高开采围岩控制难点,建立了超大采高采场“叠合拱−梁”结构模型,提出了“主动支撑防护+区域卸压弱化+全方位监测预警”三位一体围岩控制策略,验证了10 m超大采高开采围岩控制效果。研究表明:多层厚硬顶板的赋存特征致使工作面矿压显现异常强烈,初采期间大面积悬顶,正常开采期间长悬顶顶板煤壁前方断裂及架后弯曲下沉造成工作面强动载来压明显。超大采高采场“叠合拱−梁”结构力学模型计算结果及已采工作面矿压数据表明,超大采高开采所需支架支护强度将达到2 MPa以上,现有支护装备难以有效实现工作面围岩控制,降低来压步距、弱化来压动载、防止煤壁片帮及防止工作面压架是10 m超大采高采场围岩控制的关键;液压支架“双层伸缩梁+三级护帮”结构实现了对架前空顶及超高煤壁防护的独立运行,解决了原有分体式护帮煤壁防护不全面的问题,高初撑力高工作阻力液压支架明显降低了工作面煤壁片帮冒顶概率,有效缓解了来压期间顶板下沉量;井下深孔5.0 m3/min大流量定向压裂弱化技术实现了多层厚硬顶板弱化,有效降低了工作面来压强度,控制了来压期间煤壁片帮量及顶板大幅度下沉,防止工作面压架;全方位监测预警有效保障了工作面开采期间支架支撑效率,实现了顶板破断的实时跟踪及强矿压的实时分析;超大采高工作面初采期间大面积悬顶及小型飓风问题得以解决,初次来压步距为49.35 m,来压持续距离为5.75 m,支架立柱安全阀开启比例为24.81%,周期来压期间矿压显现程度得到了明显缓解,液压支架立柱平均下缩量均值由0.48 m降至0.32 m,降幅达33.3%,最大下缩量由1.88 m降至1.44 m,降幅达23.4%,工作面周期来压平均动载系数大于1.5的占比由39.6%降至14%,工作面正常生产期间煤壁片帮处于可控范围内,煤壁片帮量集中于0.2~0.5 m。该研究成果对超大采高开采围岩控制具有重要的指导意义。

     

    Abstract: The 10 m ultra-large mining height of Caojiatan Coal Mine is a world's first in terms of single mining height and mining intensity, and the effective control of surrounding rock in the stope is crucial for safe and efficient mining at the working face. Based on the analysis of the coal seam occurrence conditions and the characteristics of the ground pressure behavior of the already mined faces, and considering the ultra-large mining space and the ultra-high coal wall characteristics of the working face, the difficulties in controlling the surrounding rock of ultra-large mining height were clarified. A “superimposed arch-beam” structural model for the ultra-large mining height stope was established, and a three-in-one surrounding rock control strategy of “active support protection + regional pressure relief weakening + comprehensive monitoring and early warning” was proposed, verifying the effectiveness of the surrounding rock control for the 10 m ultra-large mining height. The research shows that: the occurrence characteristics of multi-layer thick and hard roofs cause abnormally strong mine pressure manifestation at the working face, with large-area hanging roofs during initial mining and significant strong dynamic loading pressure at the working face during normal mining. The keys to controlling the surrounding rock in the 10 m ultra-large mining height stope are reducing the pressure step distance, weakening the dynamic loading pressure, preventing rib spalling, and preventing the working face from being crushed by the pressure. The “double-layer telescopic beams + three-stage rib protection” structure of the hydraulic support achieves independent operation for the protection of the empty roof in front of the support and the ultra-high coal wall, solving the problem of incomplete rib protection by the original split-type rib protection. The high initial setting force and high working resistance of the hydraulic support significantly reduce the risk of rib spalling and roof caving at the working face and effectively control the roof subsidence during the pressure period. The underground deep-hole 5.0 m3/min high-flow directional fracturing weakening technology achieves weakening of the multi-layer thick and hard roofs, effectively reducing the intensity of mine pressure at the working face, controlling the amount of rib spalling and significant roof subsidence during the pressure period, and preventing the working face from being crushed by the pressure. Comprehensive monitoring and early warning effectively ensures the support efficiency of the support during mining, realizing real-time tracking of roof fracture and real-time analysis of strong mine pressure. The problems of large-area hanging roofs and small hurricanes during the initial mining of the ultra-large mining height working face have been resolved. The initial pressure step distance is 49.35 m, the pressure duration distance is 5.75 m, and the opening ratio of the safety valve of the support column is 24.81%. The manifestation of mine pressure during the periodic pressure period has been significantly alleviated. The average shrinkage of the hydraulic support column has decreased from 0.48 m to 0.32 m, a decrease of 33.3%, and the maximum shrinkage has decreased from 1.88 m to 1.44 m, a decrease of 23.4%. The proportion of the average dynamic load coefficient of the working face periodic pressure greater than 1.5 has decreased from 39.6% to 14%. During normal production at the working face, rib spalling is within a controllable range, with the amount of rib spalling concentrated at 0.2~0.5 m. The research results have important guiding significance for the control of surrounding rock in ultra-large mining height mining.

     

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