多层厚硬顶板大采高综放工作面强动载矿压特征及机理

Characteristics and mechanism of strong dynamic load mine pressure in large mining height full-mechanized caving face with multiple thick and hard roof

  • 摘要: 针对榆神矿区特厚煤层多层厚硬顶板大采高综放工作面下开采液压支架立柱急剧下缩、工作面易压架等强矿压显现问题,采用立柱压力传感器和位移传感器对工作面回采期间支架工作阻力、顶板下沉量进行了全程系统监测;对工作面矿压显现宏观特征、近远场覆岩运移与矿压的联动性进行了分析,明确了多层厚硬顶板大采高综放开采工作面矿压显现特征,得到了多层厚硬顶板破断的空间形态及覆岩结构演化规律;阐述了矿压作用机制,建立了考虑煤壁前方弯曲变形、多层厚硬顶板各层位间受力关联下的低、中、高不同层位覆岩结构力学模型,给出了不同层位岩层破断失稳判据及支架临界支护强度。结果表明:多层厚硬顶板大采高综放开采工作面除具有“来压区域性明显、来压急增阻、大小周期来压、周期性强动载来压”的特点外,还呈现出强动载来压期间多次连续性或短距间断性大周期来压的新特征;强动载期间连续性大周期来压矿压显现程度总体呈先增大后减缓的趋势,工作面周期性强动载来压呈不规律性,每隔4~10个小周期来压,间隔120.9~241.9 m,平均161 m发生1次强动载来压,强动载来压期间矿压显现异常强烈;上覆岩层呈现“低位悬臂梁+中位非铰接梁+高位联贯破断叠合铰接梁结构”,低位悬臂梁结构位于煤层上方20 m以内,该结构的周期性回转破断造成工作面小周期来压,中位非铰接梁位于煤层上方20~70 m范围,该范围内岩层的架前拉伸破断或架后剪切破断导致工作面发生大周期来压,高位岩层位于煤层上方70 m以上,中部厚硬岩层破断后,对高位铰接梁有效接触及支撑力减小,造成高位铰接梁相继破断失稳,继而导致工作面多次连续性或短距间断性大周期来压的强动载来压;中位非铰接梁结构破断失稳时支架合理支护强度为1.897 MPa,高位联贯破断铰接梁回转变形失稳对应的支架合理支护强度为2.470 MPa,滑落失稳对应的支架合理支护强度为3.180 MPa,现有的高强度支架难以对顶板的强矿压进行有效控制,须采取顶板弱化的手段进行采场围岩控制。研究成果对特厚煤层多层厚硬顶板开采围岩控制具有一定的指导意义。

     

    Abstract: In view of the problems of strong mine pressure such as rapid shrinkage of hydraulic support column and easy support crushing in working face under the fully mechanized caving face with large mining height in multi-layer thick and hard roof of extra-thick coal seam in Yushen mining area, the support working resistance and roof subsidence during the mining period of the working face are systematically monitored by using column pressure sensor and displacement sensor, and the macroscopic characteristics of mine pressure behavior and the linkage between near and far field overburden movement and mine pressure are analyzed. The characteristics of mine pressure in fully mechanized caving face with large mining height and multi-layer thick and hard roof were clarified, the spatial form of multi-layer thick and hard roof breaking and the evolution law of overburden structure were obtained, and the mechanism of mine pressure was expounded. The mechanical model of overburden structure in different layers of low, medium and high layers was established considering the bending deformation in front of the coal wall and the stress correlation between the layers of multi-layer thick and hard roof, The criterion of rock failure instability and the critical support strength of the support in different layers were given.The results show that the mining of fully mechanized top coal caving face with multi-layer thick and hard roof and large mining height not only has the characteristics of ‘obvious regional pressure, rapid increase of pressure resistance, large and small periodic pressure, periodic strong dynamic load pressure’, but also presents the new characteristics of multiple continuous or short-distance intermittent large periodic pressure during strong dynamic load pressure.During the period of strong dynamic load, the degree of continuous large-period rock pressure shows a trend of increasing first and then decreasing,the periodic strong dynamic load pressure of the working face is irregular, with 4 to 10 small cycles,an interval of 120.9−241.9 m and an average interval of 161 m, During the period of strong dynamic load pressure, the mine pressure appears abnormally strong.The high-level rock stratum is located more than 70 m above the coal seam. After the thick and hard rock stratum in the middle is broken, the effective contact and support force of the high-level “hinged beam” is reduced, resulting in the failure and instability of the high-level hinged beam, which in turn leads to the strong dynamic load pressure phenomenon of multiple continuous or short-distance intermittent large-cycle pressure in the working face. The reasonable support strength of the support is 1.897 MPa when the middle “non-articulated beam” structure is broken and unstable. The reasonable support strength of the support corresponding to the rotary deformation instability of the “hinged beam” is 2.470 MPa, and the reasonable support strength of the support corresponding to the sliding instability is 3.180 MPa. The existing high-strength support is difficult to effectively control the strong mine pressure of the roof. It is necessary to adopt the means of roof weakening to control the surrounding rock of the stope. The research results have important guiding significance for the surrounding rock control of multi-layer thick and hard roof mining in extra thick coal seam.

     

/

返回文章
返回