【摘要】：“高產(chǎn)高效,綠色安全”是煤炭企業(yè)的追求目標(biāo)。西部大煤田的開(kāi)發(fā)以及采煤深度的遞增,所發(fā)現(xiàn)的堅(jiān)硬煤層也越來(lái)越多,而開(kāi)采堅(jiān)硬煤層存在截齒消耗大、割煤效率低、塊煤含量低、煤塵濃度大等問(wèn)題,嚴(yán)重制約著煤炭企業(yè)的高產(chǎn)高效與生產(chǎn)安全�；诖�,本文利用水力致裂技術(shù)預(yù)先對(duì)堅(jiān)硬煤層塊裂改造,通過(guò)發(fā)揮支承壓力的碎裂作用實(shí)現(xiàn)堅(jiān)硬煤層的弱化。(1)對(duì)煤巖體水力裂縫的開(kāi)裂及擴(kuò)展行為進(jìn)行分析。基于彈性力學(xué)孔口圍巖應(yīng)力解,得出完整孔壁的開(kāi)裂壓力及方向,利用復(fù)變函數(shù)保角變換,將圓形孔邊對(duì)稱裂紋映射在數(shù)學(xué)平面的單位圓內(nèi)部,以遠(yuǎn)場(chǎng)地應(yīng)力及內(nèi)部水壓為邊界條件,得出了裂紋尖端應(yīng)力強(qiáng)度因子表達(dá)式。采用斷裂力學(xué)K判據(jù),推導(dǎo)裂縫尖端擴(kuò)展壓力。結(jié)合流體力學(xué)Navier-Stokes方程導(dǎo)出水在裂縫內(nèi)的壓降方程,推導(dǎo)了孔底水壓力與起裂長(zhǎng)度之間的關(guān)系表達(dá)式;(2)水力裂縫在堅(jiān)硬煤層中的開(kāi)裂及擴(kuò)展行為,是水力裂縫改造堅(jiān)硬煤層的前提條件。采用定向切槽只是降低起裂壓力、控制開(kāi)裂方向的一項(xiàng)措施,旨在對(duì)堅(jiān)硬煤層的塊裂改造。水在堅(jiān)硬煤層鉆孔及裂縫面邊界上的滲透過(guò)程,只起到輔助軟化作用。而經(jīng)過(guò)塊裂改造和滲透軟化的煤層,為發(fā)揮支承壓力的碎裂作用創(chuàng)造了條件�；诳箟簭�(qiáng)度的尺寸效應(yīng)和寬高比,得出了發(fā)生碎裂作用的水力鉆孔間距公式;(3)隨著采面的推進(jìn),支承壓力的遍歷促使堅(jiān)硬煤層碎裂。弱化后的堅(jiān)硬煤層,削弱了截齒與煤體的研磨作用,實(shí)現(xiàn)堅(jiān)硬煤層快速回采的同時(shí),對(duì)提高塊煤率、降低截齒消耗、降低煤塵濃度均起到一定的作用。以檸條塔煤礦南翼2-2煤S1201綜采工作面為背景,設(shè)計(jì)了水力致裂施工方案。
[Abstract]:"High yield and high efficiency, green safety" is the goal of coal enterprises. With the development of large coal fields in the west and the increasing mining depth, more and more hard coal seams have been found. However, there are some problems in mining hard coal seams, such as high cutting consumption, low cutting efficiency, low mass coal content and high dust concentration. Seriously restricts the coal enterprise high production efficiency and the production safety. Based on this, this paper uses hydraulic fracturing technology to pre-transform the hard coal seam, and realizes the weakening of hard coal seam by giving full play to the fragmentation of supporting pressure. (1) the cracking and spreading behavior of hydraulic crack in coal and rock mass are analyzed. Based on the stress solution of surrounding rock at the orifice of elastic mechanics, the crack pressure and direction of the intact hole wall are obtained. Using the conformal transformation of complex variable function, the symmetric crack of circular hole edge is mapped in the unit circle of mathematical plane. The expression of stress intensity factor at crack tip is obtained by taking the far field ground stress and internal water pressure as boundary conditions. The crack tip propagation pressure is derived by using K criterion of fracture mechanics. Combined with the Navier-Stokes equation of fluid mechanics, the pressure drop equation of water in fracture is derived, and the relation between the pressure of hole bottom water and the initiation length of crack is derived. (2) the cracking and spreading behavior of hydraulic crack in hard coal seam. It is a precondition for hydraulic crack to transform hard coal seam. The adoption of directional cutting is only a measure to reduce the initiation pressure and control the crack direction in order to reform the block crack of hard coal seam. The permeation process of water in hard coal seam drilling and fracture surface boundary only plays an auxiliary softening role. The coal seams with block cracking and permeability softening create conditions for the fragmentation of bearing pressure. Based on the dimension effect of compressive strength and the ratio of width to height, a formula for the spacing of hydraulic boreholes is obtained. (3) with the advance of mining face, the traversal of bearing pressure causes the hard coal seam to break. After weakening the hard coal seam, it weakens the grinding action of cutting teeth and coal body, and realizes the quick mining of hard coal seam, at the same time, it plays a certain role in raising block coal rate, reducing tooth cutting consumption and reducing coal dust concentration. Based on the fully mechanized coal face S1201 of 2-2 coal in the south wing of Caragana Tower Coal Mine, the hydraulic fracturing construction scheme is designed.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TD821

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