【摘要】：煤巖體是典型的裂隙巖體。我國作為世界煤炭大國,煤炭儲量豐富。近年來,隨著煤礦開采規(guī)模及開采強度的逐年加大,沖擊地壓、煤與瓦斯突出、頂板大面積垮落等煤巖動力災害日益頻繁與嚴重。水壓致裂技術是煤礦利用煤巖體的裂隙網(wǎng)絡形成水力通道來改善堅硬厚頂煤冒放性、處理堅硬頂板、進行煤巖體強度弱化從而防治沖擊礦壓、瓦斯突出和提高瓦斯抽采效率等有效技術途徑,在生產(chǎn)一線得到廣泛應用。煤層定向水壓致裂是在水壓致裂技術基礎上,利用煤巖體內(nèi)富含裂隙的特點,根據(jù)鉆孔圓周面上的徑向孔壁裂隙首先起裂的原理,通過水力割縫或者鉆頭切槽割縫技術,形成定向裂隙,引導巖層注水時破壞位置與經(jīng)典彈塑性理論相比發(fā)生偏移,使定向裂隙作為主要滲流通道對巖層進行破壞,達到控制巖層破壞的目的。神華集團新疆大洪溝煤礦分段高度約20m,工程實踐中擬采用定向水壓致裂使頂煤被充分破壞,保障安全生產(chǎn)、提高煤炭產(chǎn)量。本文以此為工程背景,對大段高頂煤進行定向水壓致裂機理研究。在研究過程中,綜合利用現(xiàn)代力學理論、實驗研究、數(shù)值分析和現(xiàn)場試驗等手段對定向裂隙起裂機理、擴展機理以及高壓水在定向裂隙中的滲流規(guī)律進行分析,得到以下成果:(1)建立定向水壓致裂力學模型,明確了定向裂隙起裂的主要影響因素包括側壓系數(shù)、圍巖壓力、裂隙長度、孔徑、裂隙尖端的曲率半徑以及裂隙傾角,及其相互影響關系。(2)以定向水壓致裂模型為基礎,完善了定向裂隙擴展力學模型,得出了定向裂隙擴展長度計算公式,提出大段高頂煤定向裂隙擴展控制方法。(3)分析了定向水壓致裂中的定向裂隙滲流分區(qū)特點,闡明了在應力—滲流條件下的定向裂隙與周圍裂隙相互作用規(guī)律。研究成果在神華集團大洪溝煤礦大段高頂煤中進行數(shù)值模擬試驗和現(xiàn)場試驗,試驗結果表明:定向水壓致裂能有效弱化煤巖體的整體力學性能,擴大頂煤破碎范圍,突出頂煤破碎效果,工作面回收率提高了10%,原煤產(chǎn)量增加,原煤連續(xù)時間增加,粉塵濃度顯著降低。
[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.
【學位授予單位】：西安科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TD32

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