余吾煤矿掘进工作面千米钻机抽采钻孔稳定性与优化布置研究

发布时间：2018-03-08 10:12

本文选题：瓦斯抽采　切入点：松软煤体　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：采用定向长钻孔抽采煤层瓦斯是煤矿井下区域瓦斯治理的有效手段之一,而我国松软煤层分布广泛,钻孔过程中塌孔事故时有发生,极大地降低了成孔率和瓦斯抽采治理的效果。因此,钻孔稳定性问题是值得深入研究的重要课题,文中以山西长治余吾煤矿掘进工作面抽采钻孔为研究对象,通过弹塑性力学理论分析、有限元数值模拟和实例计算的研究方法,围绕钻孔塌孔机理展开研究,并基于研究结果优化钻孔布置方式和钻孔轨迹设计方法。主要结论如下:(1)建立了考虑岩石应变软化特性的弹塑性力学模型,得到该力学模型下钻孔围岩弹塑性解;理论计算表明余吾煤矿松软煤体钻孔的塑性区半径为钻孔半径的1.99倍,巷道塑性区半径和应力影响半径的平均值分别为5.02m和17.09m,且分别是巷道等效半径的2.01倍和6.84倍。根据解析解提出了软化综合系数N,其值是煤岩体抗剪强度特性参数、变形特性参数和原岩应力的函数;将N作为钻孔失稳破坏的指标,表征孔壁软化程度,其值越大钻孔越容易失稳;确定的煤岩体存在临界值,当钻孔围岩达到临界值时,即出现破裂区,进而失稳破坏;余吾煤矿煤层钻孔围岩软化综合系数的临界值为2.5。(2)运用COMSOL Multiphysics多物理场耦合分析软件对钻孔围岩应力应变规律进行模拟研究得到:煤岩体强度越低、原始瓦斯压力越大、钻孔半径越大、抽采时间越长,钻孔围岩塑性区越大,钻孔稳定性相对越差;钻孔开挖后,孔壁围岩切向应力距钻孔中心2.3r左右达到应力峰值,应力集中系数均小于2;当地应力侧压系数不为1时,钻孔围岩塑性区和应力不再呈现圆形分布,余吾煤矿抽采钻孔在水平方向上孔壁两侧更容易产生应力集中、导致破坏,塑性区域呈长轴在水平方向的椭圆状。(3)通过对弹塑性力学模型及其解析解和数值模拟结果综合比较分析得到钻孔塌孔机理:钻孔围岩应变软化效应导致煤体强度下降;瓦斯压力和吸附膨胀应力下降,引起钻孔围岩有效应力急剧增大和应力集中;当应力超过煤体极限强度时,钻孔围岩产生极不稳定的破碎区,进而发生塌孔。(4)基于塌孔机理及钻孔围岩弹塑性区应力应变变化规律,为了预防塌孔,结合余吾煤矿S2108掘进工作面采掘条件,提出了采用顶(底)板梳状定向长钻孔“横向”或“纵向”布置方式掩护预抽掘进巷道围岩瓦斯方案,亦即将抽采主孔布置在稳定的岩层中,分支孔则深入煤层从而保证抽采效果。(5)针对顶(底)板梳状定向长钻孔,提出了“直线—圆弧—直线”三段式斜平面钻孔轨迹设计方法,将空间钻孔轴线简化转换至平面内设计,简单快捷,满足工程精度。(6)提出的钻孔布置方式与钻孔轨迹设计方法很好地指导了余吾煤矿煤层瓦斯治理,对于类似的煤层具有推广意义。
[Abstract]:It is one of the effective means of gas control in underground coal mine to use directional long borehole to drain coal seam. However, the loose and soft coal seam is widely distributed in our country, and the hole collapse accident occurs frequently in the process of borehole drilling. Therefore, the problem of borehole stability is an important subject worthy of further study. In this paper, the drainage borehole in the excavation face of Changzhi Yuwu Coal Mine in Shanxi Province is taken as the research object. Based on the theoretical analysis of elastic-plastic mechanics, finite element numerical simulation and example calculation, the mechanism of hole collapse in boreholes is studied. Based on the research results, the drilling layout and trajectory design method are optimized. The main conclusions are as follows: 1) the elastoplastic model considering the strain softening characteristics of rock is established, and the elastoplastic solution of the borehole surrounding rock under the model is obtained. Theoretical calculation shows that the radius of plastic zone of soft coal body in Yuwu coal mine is 1.99 times of that of borehole. The average values of plastic zone radius and stress influence radius of roadway are 5.02 m and 17.09 m, respectively, and are 2.01 and 6.84 times of equivalent radius of roadway respectively. According to the analytical solution, the softening comprehensive coefficient N is put forward, which is the characteristic parameter of shear strength of coal and rock mass. The deformation characteristic parameter and the original rock stress function; take N as the borehole instability failure index, characterizes the hole wall softening degree, its value is bigger, the borehole is easier to lose the stability; the determined coal and rock mass has the critical value, when the borehole surrounding rock reaches the critical value, That is, the rupture zone appears, and then the instability is destroyed; The critical value of comprehensive coefficient of surrounding rock softening of coal seam in Yuwu coal mine is 2.5.0.The stress and strain law of borehole surrounding rock is simulated by COMSOL Multiphysics multi-physical field coupling analysis software. The lower the strength of coal and rock mass, the greater the original gas pressure. The larger the radius of the borehole, the longer the extraction time, the larger the plastic zone of the surrounding rock, the worse the stability of the borehole. The stress concentration factor is less than 2, when the stress lateral pressure coefficient is not 1:00, the plastic zone and stress of the borehole surrounding rock will no longer appear circular distribution, and the stress concentration on both sides of the hole wall in the horizontal direction is more easily produced by the extraction borehole in Yuwu Coal Mine, which leads to the destruction of the borehole wall. The plastic region is ellipsoid with long axis in the horizontal direction. By comparing and analyzing the elastoplastic mechanics model, its analytical solution and numerical simulation results, the mechanism of borehole collapse is obtained: the strain softening effect of borehole surrounding rock leads to the decrease of coal strength; The decrease of gas pressure and adsorption expansion stress leads to the sharp increase of effective stress and stress concentration in the surrounding rock of borehole, and when the stress exceeds the limit strength of coal, the rock of borehole produces extremely unstable fracture zone. Based on the mechanism of hole collapse and the rule of stress and strain variation in elastic-plastic zone of surrounding rock of borehole, in order to prevent hole from collapsing, combined with the mining condition of S _ 2108 heading face in Yuwu Coal Mine, This paper puts forward a plan to cover the surrounding rock gas of the roadway by adopting the arrangement of "transverse" or "longitudinal" arrangement of the comb-like directional long hole in the top (bottom) plate, and the main hole of the drainage will be arranged in the stable rock stratum. The branch hole goes deep into the coal seam to ensure the extraction effect. (5) aiming at the comb directional long hole of the top (bottom) plate, a three-section inclined plane drilling trajectory design method of "straight line, circular arc line" type is put forward. The method of borehole layout and borehole trajectory design, which is put forward by simplifying the axis of space drilling to plane design, is simple and quick, and satisfies the engineering precision. It can guide the gas control of coal seam in Yuwu coal mine very well. To the similar coal seam has the popularizing significance.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712.6

【相似文献】