大段高顶煤定向水压致裂机理研究
发布时间：2018-11-24 13:55
【摘要】：煤岩体是典型的裂隙岩体。我国作为世界煤炭大国,煤炭储量丰富。近年来,随着煤矿开采规模及开采强度的逐年加大,冲击地压、煤与瓦斯突出、顶板大面积垮落等煤岩动力灾害日益频繁与严重。水压致裂技术是煤矿利用煤岩体的裂隙网络形成水力通道来改善坚硬厚顶煤冒放性、处理坚硬顶板、进行煤岩体强度弱化从而防治冲击矿压、瓦斯突出和提高瓦斯抽采效率等有效技术途径,在生产一线得到广泛应用。煤层定向水压致裂是在水压致裂技术基础上,利用煤岩体内富含裂隙的特点,根据钻孔圆周面上的径向孔壁裂隙首先起裂的原理,通过水力割缝或者钻头切槽割缝技术,形成定向裂隙,引导岩层注水时破坏位置与经典弹塑性理论相比发生偏移,使定向裂隙作为主要渗流通道对岩层进行破坏,达到控制岩层破坏的目的。神华集团新疆大洪沟煤矿分段高度约20m,工程实践中拟采用定向水压致裂使顶煤被充分破坏,保障安全生产、提高煤炭产量。本文以此为工程背景,对大段高顶煤进行定向水压致裂机理研究。在研究过程中,综合利用现代力学理论、实验研究、数值分析和现场试验等手段对定向裂隙起裂机理、扩展机理以及高压水在定向裂隙中的渗流规律进行分析,得到以下成果:(1)建立定向水压致裂力学模型,明确了定向裂隙起裂的主要影响因素包括侧压系数、围岩压力、裂隙长度、孔径、裂隙尖端的曲率半径以及裂隙倾角,及其相互影响关系。(2)以定向水压致裂模型为基础,完善了定向裂隙扩展力学模型,得出了定向裂隙扩展长度计算公式,提出大段高顶煤定向裂隙扩展控制方法。(3)分析了定向水压致裂中的定向裂隙渗流分区特点,阐明了在应力—渗流条件下的定向裂隙与周围裂隙相互作用规律。研究成果在神华集团大洪沟煤矿大段高顶煤中进行数值模拟试验和现场试验,试验结果表明:定向水压致裂能有效弱化煤岩体的整体力学性能,扩大顶煤破碎范围,突出顶煤破碎效果,工作面回收率提高了10%,原煤产量增加,原煤连续时间增加,粉尘浓度显著降低。
[Abstract]:Coal rock mass is a typical fractured rock mass. As a big coal country in the world, China is rich in coal reserves. In recent years, with the coal mining scale and mining intensity increasing year by year, the impact ground pressure, coal and gas outburst, roof collapse and other coal and rock dynamic disasters become more and more frequent and serious. Hydraulic fracturing technology is used to improve the caving property of hard and thick top coal by forming hydraulic channel of coal and rock mass fracture network in coal mine, to deal with hard roof, to weaken the strength of coal and rock mass, and to prevent the impact of rock pressure. Effective technical approaches such as gas outburst and gas drainage efficiency are widely used in production line. On the basis of hydraulic fracturing technology, coal seam directional hydraulic fracturing is based on the characteristics of rich fractures in coal and rock, according to the principle that radial hole wall cracks on the borehole circumference are initiated first, and by hydraulic cutting or bit slot cutting technology. The directional fissure is formed and the failure position of the rock bed is induced to be offset compared with the classical elastic-plastic theory. The directional fissure is used as the main seepage passage to destroy the rock formation and the purpose of controlling the rock formation failure is achieved. The section height of Xinjiang Dahonggou coal mine of Shenhua Group is about 20m.The directional hydraulic fracturing is proposed in engineering practice to make the top coal be destroyed fully, to ensure safe production and to increase coal output. In this paper, based on the engineering background, the mechanism of directional hydraulic cracking of large section high top coal is studied. In the process of research, the mechanism of crack initiation, propagation and seepage of high pressure water in directional fracture are analyzed by means of modern mechanics theory, experimental research, numerical analysis and field test. The following results are obtained: (1) the mechanical model of directional hydraulic fracturing is established, and the main influencing factors of directional fracture initiation include lateral pressure coefficient, surrounding rock pressure, crack length, aperture, curvature radius of crack tip and crack dip angle. (2) based on the directional hydraulic fracturing model, the mechanical model of directional crack propagation is improved, and the formula for calculating the length of directional crack propagation is obtained. A control method for directional crack propagation of large section high top coal is proposed. (3) the characteristics of directional fracture seepage zone in directional hydraulic fracturing are analyzed, and the interaction law between directional crack and surrounding fissure under stress-seepage condition is expounded. Numerical simulation and field tests were carried out in large section of high top coal in Dayonggou Coal Mine of Shenhua Group. The results show that directional hydraulic fracturing can effectively weaken the overall mechanical properties of coal and rock mass and expand the broken range of top coal. The recovery rate of coal face is increased by 10%, the output of raw coal is increased, the continuous time of raw coal is increased, and the dust concentration is decreased significantly.
【学位授予单位】：西安科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TD32
本文编号：2353979
[Abstract]:Coal rock mass is a typical fractured rock mass. As a big coal country in the world, China is rich in coal reserves. In recent years, with the coal mining scale and mining intensity increasing year by year, the impact ground pressure, coal and gas outburst, roof collapse and other coal and rock dynamic disasters become more and more frequent and serious. Hydraulic fracturing technology is used to improve the caving property of hard and thick top coal by forming hydraulic channel of coal and rock mass fracture network in coal mine, to deal with hard roof, to weaken the strength of coal and rock mass, and to prevent the impact of rock pressure. Effective technical approaches such as gas outburst and gas drainage efficiency are widely used in production line. On the basis of hydraulic fracturing technology, coal seam directional hydraulic fracturing is based on the characteristics of rich fractures in coal and rock, according to the principle that radial hole wall cracks on the borehole circumference are initiated first, and by hydraulic cutting or bit slot cutting technology. The directional fissure is formed and the failure position of the rock bed is induced to be offset compared with the classical elastic-plastic theory. The directional fissure is used as the main seepage passage to destroy the rock formation and the purpose of controlling the rock formation failure is achieved. The section height of Xinjiang Dahonggou coal mine of Shenhua Group is about 20m.The directional hydraulic fracturing is proposed in engineering practice to make the top coal be destroyed fully, to ensure safe production and to increase coal output. In this paper, based on the engineering background, the mechanism of directional hydraulic cracking of large section high top coal is studied. In the process of research, the mechanism of crack initiation, propagation and seepage of high pressure water in directional fracture are analyzed by means of modern mechanics theory, experimental research, numerical analysis and field test. The following results are obtained: (1) the mechanical model of directional hydraulic fracturing is established, and the main influencing factors of directional fracture initiation include lateral pressure coefficient, surrounding rock pressure, crack length, aperture, curvature radius of crack tip and crack dip angle. (2) based on the directional hydraulic fracturing model, the mechanical model of directional crack propagation is improved, and the formula for calculating the length of directional crack propagation is obtained. A control method for directional crack propagation of large section high top coal is proposed. (3) the characteristics of directional fracture seepage zone in directional hydraulic fracturing are analyzed, and the interaction law between directional crack and surrounding fissure under stress-seepage condition is expounded. Numerical simulation and field tests were carried out in large section of high top coal in Dayonggou Coal Mine of Shenhua Group. The results show that directional hydraulic fracturing can effectively weaken the overall mechanical properties of coal and rock mass and expand the broken range of top coal. The recovery rate of coal face is increased by 10%, the output of raw coal is increased, the continuous time of raw coal is increased, and the dust concentration is decreased significantly.
【学位授予单位】：西安科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TD32
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