基于Burgers模型的深井采区下山保护煤柱长期稳定性研究

    Study on long-term stability of downhill protective coal pillars in deep mines based on Burgers model

    • 摘要: 深部矿井采区下山保护煤柱长期处于“三高一扰动”的复杂环境中,其蠕变损伤累积效应显著影响其长期稳定性,传统基于静力学假设的设计方法难以满足工程需求。以阳城煤矿北三采区为工程背景,针对下山保护煤柱的长期稳定性问题,提出了基于Burgers蠕变模型的数值分析方法。通过5组对比试验标定Burgers模型参数,揭示了Burgers模型各参数对瞬时蠕变量、初始蠕变速率及稳定应变量的标定规律,并验证了煤样数值模拟结果与室内蠕变试验结果的吻合性(最大误差<3.5%)。基于FLAC3D数值模拟软件构建地质力学模型,综合理论计算、静力学模拟及蠕变分析,对比了“三下”开采规范法(56.3 m)、极限平衡理论(53.7 m)及Mohr−Coulomb弹塑性模型(58.8 m)等在未考虑时间效应时的采区下山保护煤柱宽度,并进一步引入Burgers模型分析煤柱蠕变特性。模拟结果表明:保护煤柱在10年服务周期内,煤柱蠕变导致原岩应力边界向巷道方向迁移,工作面终采线与应力边界间距由58.8 m增至72.3 m,水平位移在3年后保持基本平稳,蠕变周期内累积位移约70 mm。综合考虑超前支承压力影响及蠕变损伤累积效应,最终确定北三采区下山保护煤柱合理宽度为75 m。

       

      Abstract: The protective coal pillars in the downhill sections of deep mines are long-term in a complex environment of “three highs and one disturbance”(high stress, high water pressure, high ground temperature and excavation disturbance) , and their cumulative creep damage effect significantly affects their long-term stability. Traditional design methods based on static assumptions are difficult to meet engineering requirements. Taking the north No.3 mining area of Yangcheng Coal Mine as the engineering background, aiming at the long-term stability problem of downhill protective coal pillars, a numerical analysis method based on the Burgers creep model is proposed. Five groups of comparative tests were conducted to calibrate the parameters of the Burgers model, revealing the calibration laws of each parameter of the Burgers model on the instantaneous creep deformation, initial creep rate, and stable strain, and verifying the consistency between the numerical simulation results of coal samples and the laboratory creep test results (the maximum error < 3.5%). based on the FLAC3D numerical simulation software to construct a geomechanical model, this study integrates theoretical calculation, static simulation and creep analysis to compare the widths of downhill protective coal pillars in the mining area when the time effect is not considered, including the “three unders” mining (mining under buildings, railways and water bodies) specification method (56.3 m), the limit equilibrium theory (53.7 m) and the Mohr-Coulomb elastoplastic model (58.8 m), furthermore, the Burgers model is introduced to analyze the creep characteristics of coal pillars. The simulation results show that within the 10-year service period of the protective coal pillar, creep of the coal pillar causes the in-situ stress boundary to migrate toward the roadway. The distance between the final mining line of the working face and the stress boundary increases from 58.8 m to 72.3 m, the horizontal displacement remains basically stable after 3 years, and accumulated displacement during the creep period is approximately 70 mm. Considering the influence of advance abutment pressure and the cumulative effect of creep damage comprehensively, the reasonable width of the downhill protective coal pillar in the north No.3 mining area is finally determined to be 75 m.

       

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