【作者】 崔峰；

【导师】 来兴平；

【作者基本信息】 西安科技大学 ， 采矿工程， 2014， 博士

【摘要】 复杂条件下特厚煤层综放开采的关键是提高顶煤冒放性、降低煤岩体应力集中。注水和爆破作为煤岩体致裂有效的手段得到广泛使用。煤岩体结构及其材质的天然复杂性导致煤岩体耦合致裂问题是一个涉及煤/岩-裂隙-水-爆生气体多介质互相作用的复杂过程。研究固-液耦合体的耦合致裂机制、效果优化和煤体离散化的微观参数制取等有着重要的科学意义和工程应用价值。论文以复杂环境下急倾斜煤岩体的耦合致裂为背景，采用理论分析、岩石力学实验、数值模拟、神经网络、现场监测和工业试验相结合的方法开展研究。取得的主要成果有：(1)急倾斜煤层开采环境与应力条件复杂。急倾斜煤层顶板岩体裂隙发育不显著，整体较为致密，易产生重力坍塌等动力灾害问题。工作面还面临特厚煤层的有效弱化、坚硬顶板岩石的卸压难题，涉及到采掘工作面相遇期间的应力集中、历史上小煤窑采煤情况不明、硫化氢气体以及动力灾害频发的影响，开采环境与应力条件复杂。(2)煤体冒放性的提高主要与爆破致裂产生的宏观裂隙区有关，对于某些严格控制爆破扰动的工程需将微观裂纹纳入到考虑范围内。爆炸后形成的压碎区、裂隙区与炸药性能及被爆体的物理力学特性有关，压碎区半径和裂隙区半径各自与炸药半径的比值并不会随着炸药半径的增大而增大，但压碎区和裂隙区半径随装药量的增加而加大。(3)确定了评估注水致裂强度劣化的评估指数。尺寸效应的存在使得试件破坏水压呈上升趋势，破坏水压和试件半径R/钻孔半径r呈现出较好的相关性，随着试件所需破坏范围的加大要求水压愈大。在渗透水压作用下试件破坏所需荷载减小，渗透水压较大，较早的对试件顶部产生破坏。掌握了注水致裂的劣化指数Y表征与渗透水压的关系，获得了渗透水压与试件强度和峰值荷载的表达式。(4)揭示了耦合致裂的致裂机制。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，耦合致裂效果大于两者的简单叠加。引入强度劣化率f作为评估耦合致裂效果的指标，并给出了耦合致裂技术实施时裂纹的扩展准则，获得了耦合致裂主要参数与强度劣化程度f的关系。实现了煤体整体-散体的等效转化，获得了等效耦合致裂效果的离散元细观参数，建立了不同强度煤体和放出率间的关系、耦合致裂参数与放出率的关系，垮放试验表明散体介质流理论较适用于低位放顶煤的开采。耦合致裂不仅可以降低被爆炸体的强度，还可降低整体的应力水平，减小应力分布梯度。(5)完成了煤岩体耦合致裂技术的应用与效果的定量化评估。以复杂环境下急斜特厚煤岩体的耦合致裂为背景，制定了提高煤体冒放性和实现岩体卸压的耦合致裂方案，采用神经网络完成了煤岩体耦合致裂效果的预计，并对现场工业试验中煤体的垮放情况进行记录分析，对耦合致裂后表征岩体卸压程度的微震事件进行监测，验证了神经网络预测的准确性。实践结果反映出在煤岩体的耦合致裂措施下，顶煤的冒放性和动力灾害问题均得到了较好的控制和解决。论文研究结果在促进固液耦合致裂基础研究及其效果评估方面具有较好的科学及实用价值，为形成复杂条件下特厚煤层综放工作面顶煤的耦合致裂技术提供了指引。更多还原

【Abstract】 The key to mine very thick coal seam under complicated conditions is to improve the topcoal caving and reduce stress concentration. Injecting water and blasting are widely used as aneffective means of fracturing. Because of the complex coal-rock structure and material, thecoupling fracturing problem is the complicated action of multi-media includedcoal/rock-crack-water-explosive gases. the study on the mechanism of coupling fracturing,optimization effect and microscopic parameters for discrete coal, have important scientificsignificance and application value.Centered on the coupled-crack for steeply inclined coal-rock under the complicatedenvironment, the combination of theoretical analysis, rock mechanics experiments, numericalsimulation, neura network, field monitoring and industrial test are used in this study. Themain achievement are shown as below:(1)The mining environment and stress conditions of mining steeply dipping coal seamare complicated. The fracture in roof rock has not fully developed, the roof is nearly intact,which easily leads to the gravity collapse and other dynamic disaster. Working faceencounters puzzle of effectively weaken thick coal seam and pressure relief of hard roof rock.They are related to stress concentration caused by the encounter of mining and tunneling workface, the unknown mining history by small coal mines and H2S gas and frequent dynamicdisasters, which further complicate mining environment and stress conditions.(2)The improving caving effect of coal is mainly related to the macro fracture zoneproduced by blasting, the micro crack disturbance should be considered for some strictlycontrolled blasting engineering. The crushed zone and fractured zone induced by explosionare related to the explosive performance and physical and mechanical properties of blastedbody. The crushed zone radius and crack area radius respectively divided by explosive radius does not increase with the explosive radius, but the radius of fracture zone and cracked zoneincreases with the increase of explosive weigh.(3)The strength deterioration evaluation index is proposed to evaluate hydraulicfracturing. The specimen failure pressure has an increasing intend by the action of size effect,failure pressure showes a good correlation with the valued of specimen radius (R)/boreholeradius (r), the hydraulic pressure increases with the high demand of damage range. Therequired damage load is reduced under the effect of seepage pressure, the larger seepagepressure is, the earlier the damage of top specimen occurs. The relationship of degradationindex Y and seepage pressure of inject water is derived, the expressions of specimen strengthand peak load with seepage pressure are obtained.(4)The meaning and fracturing mechanism of coupled-crack are put forward and defined.The essence of coupled-crack is that the detonation gas and shock wave formed by explosionspread in soften coal-rock. The coupled-crack effect is greater than the simple superpositionof blasting and injecting water. The strength deterioration rate f is introduced as the evaluationindex of coupled-crack effect, and the crack growth criterion in the implementation ofcoupled-crack is given, the relationship between the main coupled-crack parameters andstrength deterioration degree is obtained. The equivalent conversion of coal from integral togranular is achieved, obtaining the micromechanical parameters for equivalent coupled-crackeffect based on discrete element, the relationships of release rate with different strength coaland coupled-crack parameters are established. The caving and releasing tests showed that thegranular medium flow theory is suitable for explaining the low-position top-coal cavingmining. Coupled-crack can not only reduce the strength of coal-rock, but also can reduce theoverall stress level, reducing the stress gradient.(5)The quantitative evaluation of coal-rock coupling-fracturing effect is achieved byusing BP neural network. Taking the steeply dipping extra-thick coal-rock coupling-fracturingin complex environment as the background, the coupled fracturing scheme of improvingcaving for coal and unloading for rock mass is designed, neural network is used to evaluatethe coupled-crack effect, and the caving effect of top-coal in industrial experiment isconsidered and analysed. The microseismic events is monitored to reflect relief degree ofcoupled-crack. Field results show that the problems of top coal caving and power disasterhave been better controlled and solved by the measures of coal-rock coupled-crack.The research results have better scientific and practical value in promoting the basicresearch of solid-liquid coupling and its effect evaluation, which provides guidelines for theformation of coupling-crack technology used in top coal caving faces with very thick coal seam under the complicated conditions.更多还原