基于围岩应力差异梯度控制的深部煤巷防冲机制与技术

Mechanism and technology of rock burst prevention in deep coal tunnel based on controlling surrounding rock stress difference gradient

  • 摘要: 针对深部煤巷冲击地压灾害,以聚焦围岩垂向应力与径向水平应力差异的“煤巷围岩应力差异梯度致冲机理”为基础,探究其致冲机制,研发防冲关键技术。采用数值模拟、理论分析、现场实践等方法,从应力差异角度,分析单元体、围岩的稳定性及破坏特征,分析基于应力差异控制的防冲机制;基于Dgc区域和局部联合控制的思路,提出煤巷围岩三级改造防冲技术方案,结合母杜柴登井田30202工作面现场三级改造工程案例进行分析。结果表明:强冲击倾向性煤体能承载更高的应力差异,为补偿过高的应力差异需要更高的能量释放强度,应力差异驱动煤体偏向于脆性剪切破裂;具有冲击倾向性的煤巷围岩易因高Dgc驱动而发生失稳,强冲击倾向性煤层Dgc更大,冲击风险激增;单一强支护提升围岩强度,也导致Dg在帮部集中,Dgc更加接近冲击临界条件,增强围岩Dg升高区阻抗、降低Dgmax是防冲着力点,主动支护和被动支护以及煤层改造需要协同作用才能有效降低围岩冲击风险;经微震事件、管路压力、排出煤粉量等指标及开采实践验证,三级改造防冲技术方案相较于传统卸压技术方法具有更强的减冲效果,适用于高应力差异区的煤层改造防冲需求,一级区域压裂改构和二级区域注水改性显著降低煤巷围岩的应力差异程度,巷道冲击危险等级降低,三级卸压钻孔间距可适当增加,减小工程量。

     

    Abstract: In view of the rock burst disaster of deep coal roadway, explore the rock burst mechanism and develop the key prevention technology, based on the “Mechanism of rock burst in deep coal tunnel surroundings due to stress difference gradient” which attaches importance to the influence of horizontal stress. The stability of unit body and surrounding rock, the damage characteristics and prevention mechanism of rock burst from the perspective of stress difference are analyzed with the method of numerical simulation, theoretical analysis, on-site practice in this paper. Based on the thought of regional and local Dgc combined controlling, put forward the three-stage transformation of coal tunnel surrounding rock prevention technology program. The engineering case of 30202 working face in Muduchaideng coal mine is analyzed. The results show that: Strong rock burst propensity coal body can carry higher Δσ, in order to compensate for the excessive Δσ requires a higher intensity of energy release, Δσ drive the coal body is biased towards brittle shear rupture; Coal bodies with rock burst propensity are prone to destabilization driven by high Dgc. With the rock burst propensity increases, the Dgc value shows an increasing trend, especially in the strong rock burst propensity coal seam, high Dgc value makes the surrounding rock burst risk surge; Enhance the impedance of the Dg elevation area, weaken the Dgmax value is the focus of anti-rock explosion. Strong support in the enhancement of the strength of the coal body, but also lead to the concentration of Dg in the gang, the Dgc value is closer to the critical conditions of rock explosion. Active support and passive support and coal seam modification need combined effect to reduce the rock burst risk effectively. The first level of regional fracturing reconstruction and the second level of regional water injection modification technology can significantly reduce the Δσ value, when the rock explosion risk level of the coal body is reduced. Therefore, the spacing of drill holes in the third level can be increased appropriately. After the validation of microseismical system, pipeline pressure, coal dust volume and other indexes and practical test, this technical solution has stronger modification effect compared with traditional technical methods, and it is also more suitable for the demand of coal seam modification in high Δσ area.

     

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