煤体耦合致裂后整体–散体的等效转化及其垮放能力评估

INTACT-LOOSE MEDIUM EQUIVALENT TRANSFORMATION AFTER COUPLED CRACKING AND ASSESSMENT OF CAVING CAPABILITY

以耦合致裂效果定量化评估为目标,采用数值模拟的方法构建等效于煤体耦合致裂后强度的离散元模型。提出以模型整体强度为指标实现煤体整体–散体的等效离散化转化,利用离散元模型研究顶煤的垮放、流动规律,分析耦合致裂后离散态颗粒间的铰接关系及其对垮放程度的影响,量化装药量、注水压力和煤体垮放能力之间的映射关系,通过工程实践进行验证。结果表明:耦合致裂的本质是爆炸形成的爆生气体和冲击波共同在已软化的煤岩体中传播,以煤体整体的强度为等效转化指标实现研究对象在不同算法间的等效转化。耦合致裂通过降低块体间拉应力和颗粒间接触的数量提高煤体的冒放性,得出煤体充分垮放指标和满足厚煤层采区回采率要求的强度最高值,完成复杂环境下煤体耦合致裂效果的定量化评估。

A discrete element model(DEM) of describing the equivalent strength of coal mass after cracking due to the coupled action was established for the quantitative evaluation of the effect of cracking due to coupled action. The overall strength was taken as an index to achieve the equivalent transformation of discretization of intact to loose coal mass. The caving of the top coal and the flow pattern were researched with DEM. The hinge relationship of discrete particles and its influence to caving after coupled cracking were analyzed. The relationship between the caving and flowing capacity of coal mass,the parameters of explosive load and the injecting pressure of water was quantified and the result was verified in an engineering practice. The essence of coupled cracking was the spreading of the gas and blast wave generated in the explosion in the softened coal-rock. The overall strength of coal-mass was regarded as an equivalent conversion index for the equivalent transformation between the different algorithms for coal-mass. The method of coupled cracking increased the caving effect of coal-mass by reducing the tensile stress of blocks and the amount of contact between particles. The strength of coal mass for fully caving and the peak strength meeting the requirements of recovery ratio for the thick coal seam were obtained. The quantitative assessment of coupled cracking in coal mass under the complex environment was accomplished.