發(fā)布時間：2018-12-17 08:04

【摘要】：松軟高瓦斯煤層在我國分布廣。我國煤與瓦斯動力災(zāi)害產(chǎn)生的“溫床”就是松軟煤層，其防治措施主要是井下鉆孔預(yù)抽瓦斯。受煤體硬度小的影響，松軟煤層瓦斯抽采鉆孔易變形、坍塌，極大降低了瓦斯抽采效率，嚴(yán)重限制了礦井瓦斯抽采達標(biāo)進程。本文以松軟煤層瓦斯抽采鉆孔失穩(wěn)為研究對象，通過理論模型、數(shù)值模擬、相似實驗和現(xiàn)場試驗的方法，對松軟煤層坍塌失效機制和控制方法開展了系統(tǒng)的理論和技術(shù)研究。 建立了基于孔隙流體滲流的鉆孔坍塌失效的線彈性模型，得出了松軟煤層坍塌壓力隨瓦斯?jié)B流的衰減規(guī)律，，分析了煤層基本力學(xué)參數(shù)、流體滲流和鉆孔軌跡的空間方位等因素對鉆孔坍塌失效的影響：①對于煤層流體壓力大的鉆孔，初始坍塌風(fēng)險大，但坍塌壓力衰減的速率快，到達穩(wěn)定的時間短，應(yīng)在其抽采初期對孔壁加強臨時支護；②當(dāng)鉆孔傾角小于60°時，鉆孔方位角為35°的鉆孔穩(wěn)定性最差；當(dāng)鉆孔傾角大于60°時鉆孔方位角為90°的鉆孔穩(wěn)定性最差；③對于鉆進需要穿過軟弱夾層、復(fù)雜地質(zhì)構(gòu)造帶的鉆孔，鉆進角度調(diào)整為22.5°時最穩(wěn)定。 考慮損傷對煤體破壞過程力學(xué)參數(shù)的影響，引入能夠反映軟煤加速蠕變的非線性蠕變元件，建立了軟煤粘彈塑性非線性蠕變本構(gòu)方程。結(jié)合實驗室松軟煤體原煤試樣的單軸壓縮蠕變試驗對蠕變元件的流變參數(shù)進行了辨識，探討了關(guān)鍵元件的特征參數(shù)對模型蠕變特性的影響規(guī)律。 研究了裸孔和支護鉆孔圍巖應(yīng)力場及其蠕變特性，分析了埋深、側(cè)壓系數(shù)、孔隙壓力等參數(shù)對鉆孔變形破壞的影響規(guī)律：①埋深超過600m以后鉆孔圍巖蠕變速度開始加快，垂直位移及塑性區(qū)范圍急劇增大，鉆孔開始縮徑。②當(dāng)側(cè)壓系數(shù)超過1.2以后，最大主應(yīng)力與最小主應(yīng)力差值在頂、底部，容易造成煤體剪切破壞而塌孔。③孔隙壓力的增加，會造成鉆孔圍巖垂直位移也逐漸增加，但對最大垂直應(yīng)力最大值和塑性區(qū)的發(fā)展影響不大。④隨著護孔管支撐強度的增加，圍巖垂直位移逐漸減小，聲發(fā)射信號強度減弱，鉆孔垂直應(yīng)力集中系數(shù)和最大垂直應(yīng)力作用點與孔壁距離減小。 依據(jù)鉆孔的形變程度對瓦斯抽采流量的影響，將鉆孔穩(wěn)定性進行了等級劃分。針對Ⅱ級、Ⅲ級和Ⅳ級鉆孔提出了“協(xié)同式”、“分步式”和“推進式”護孔方法。開發(fā)出了磁吸牙片限位反轉(zhuǎn)式鉆頭和內(nèi)附導(dǎo)向襯管式鉆桿，現(xiàn)場試驗了協(xié)同式鉆護體化技術(shù)。結(jié)果表明，使用新技術(shù)的鉆孔單孔平均百米純流量比礦方工藝鉆孔提高了2倍。
[Abstract]:Soft and high gas seams are widely distributed in China. The "hotbed" produced by coal and gas dynamic disasters in China is soft coal seam. Influenced by the small hardness of coal body, the borehole of gas drainage in soft coal seam is easy to deform and collapse, which greatly reduces the efficiency of gas extraction and seriously limits the process of reaching the standard of gas drainage in coal mine. In this paper, the failure mechanism and control method of soft coal seam collapse are studied systematically by means of theoretical model, numerical simulation, similarity experiment and field test. The linear elastic model of borehole collapse failure based on pore fluid seepage is established, and the attenuation law of collapse pressure with gas seepage in soft coal seam is obtained, and the basic mechanical parameters of coal seam are analyzed. The effects of fluid percolation and space orientation of borehole trajectory on borehole collapse failure are as follows: 1 for boreholes with high fluid pressure in coal seam, the initial collapse risk is high, but the rate of collapse pressure attenuation is fast, and the time to reach stability is short. The temporary support for the hole wall should be strengthened in the early stage of its extraction. 2When the borehole inclination angle is less than 60 擄, the borehole stability is the worst when the borehole azimuth angle is 35 擄, the borehole stability is the worst when the borehole inclination angle is greater than 60 擄and the borehole azimuth angle is 90 擄when the borehole inclination angle is greater than 60 擄. (3) for drilling holes which need to pass through weak intercalation and complex geological structural zone, the drilling angle is the most stable when the drilling angle is adjusted to 22.5 擄. Considering the influence of damage on the mechanical parameters of coal mass failure process, a nonlinear creep element which can reflect the accelerated creep of soft coal is introduced, and the constitutive equation of elastoplastic nonlinear creep of soft coal is established. The rheological parameters of creep elements are identified by uniaxial compression creep test of raw coal samples of soft coal body in laboratory, and the influence of characteristic parameters of key components on creep characteristics of the model is discussed. The stress field and creep characteristics of surrounding rock of bare hole and supporting borehole are studied. The influence of parameters such as depth of burying, coefficient of lateral pressure and pore pressure on the deformation and failure of borehole is analyzed: (1) the creep velocity of surrounding rock of borehole begins to accelerate when the depth of buried is more than 600m. The range of vertical displacement and plastic zone increases sharply, and the borehole begins to shrink. 2 when the lateral pressure coefficient exceeds 1.2, the difference between the maximum principal stress and the minimum principal stress is at the top and bottom, It is easy to cause shear failure of coal body and collapse hole. 3 the increase of pore pressure will cause the vertical displacement of surrounding rock of borehole to increase gradually, but it has little effect on the maximum vertical stress and the development of plastic zone. The vertical displacement of surrounding rock decreases gradually, the intensity of acoustic emission signal weakens, and the vertical stress concentration factor of borehole and the distance between the maximum vertical stress and the hole wall decrease. According to the influence of borehole deformation degree on gas drainage discharge, the stability of borehole is classified. This paper puts forward "cooperative type", "step type" and "propulsive" method for drilling of grade 鈪

本文編號：2383931