松软煤层瓦斯抽采钻孔塌孔失效特性及控制技术基础
发布时间：2018-12-17 08:04
【摘要】：松软高瓦斯煤层在我国分布广。我国煤与瓦斯动力灾害产生的“温床”就是松软煤层，其防治措施主要是井下钻孔预抽瓦斯。受煤体硬度小的影响，松软煤层瓦斯抽采钻孔易变形、坍塌，极大降低了瓦斯抽采效率，严重限制了矿井瓦斯抽采达标进程。本文以松软煤层瓦斯抽采钻孔失稳为研究对象，通过理论模型、数值模拟、相似实验和现场试验的方法，对松软煤层坍塌失效机制和控制方法开展了系统的理论和技术研究。 建立了基于孔隙流体渗流的钻孔坍塌失效的线弹性模型，得出了松软煤层坍塌压力随瓦斯渗流的衰减规律，，分析了煤层基本力学参数、流体渗流和钻孔轨迹的空间方位等因素对钻孔坍塌失效的影响：①对于煤层流体压力大的钻孔，初始坍塌风险大，但坍塌压力衰减的速率快，到达稳定的时间短，应在其抽采初期对孔壁加强临时支护；②当钻孔倾角小于60°时，钻孔方位角为35°的钻孔稳定性最差；当钻孔倾角大于60°时钻孔方位角为90°的钻孔稳定性最差；③对于钻进需要穿过软弱夹层、复杂地质构造带的钻孔，钻进角度调整为22.5°时最稳定。 考虑损伤对煤体破坏过程力学参数的影响，引入能够反映软煤加速蠕变的非线性蠕变元件，建立了软煤粘弹塑性非线性蠕变本构方程。结合实验室松软煤体原煤试样的单轴压缩蠕变试验对蠕变元件的流变参数进行了辨识，探讨了关键元件的特征参数对模型蠕变特性的影响规律。 研究了裸孔和支护钻孔围岩应力场及其蠕变特性，分析了埋深、侧压系数、孔隙压力等参数对钻孔变形破坏的影响规律：①埋深超过600m以后钻孔围岩蠕变速度开始加快，垂直位移及塑性区范围急剧增大，钻孔开始缩径。②当侧压系数超过1.2以后，最大主应力与最小主应力差值在顶、底部，容易造成煤体剪切破坏而塌孔。③孔隙压力的增加，会造成钻孔围岩垂直位移也逐渐增加，但对最大垂直应力最大值和塑性区的发展影响不大。④随着护孔管支撑强度的增加，围岩垂直位移逐渐减小，声发射信号强度减弱，钻孔垂直应力集中系数和最大垂直应力作用点与孔壁距离减小。 依据钻孔的形变程度对瓦斯抽采流量的影响，将钻孔稳定性进行了等级划分。针对Ⅱ级、Ⅲ级和Ⅳ级钻孔提出了“协同式”、“分步式”和“推进式”护孔方法。开发出了磁吸牙片限位反转式钻头和内附导向衬管式钻杆，现场试验了协同式钻护体化技术。结果表明，使用新技术的钻孔单孔平均百米纯流量比矿方工艺钻孔提高了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 掳, the borehole stability is the worst when the borehole azimuth angle is 35 掳, the borehole stability is the worst when the borehole inclination angle is greater than 60 掳and the borehole azimuth angle is 90 掳when the borehole inclination angle is greater than 60 掳. (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 掳. 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
本文编号：2383931
[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 掳, the borehole stability is the worst when the borehole azimuth angle is 35 掳, the borehole stability is the worst when the borehole inclination angle is greater than 60 掳and the borehole azimuth angle is 90 掳when the borehole inclination angle is greater than 60 掳. (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 掳. 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
本文编号：2383931
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