流固应力耦合作用下的软煤钻孔失稳特征研究

发布时间：2018-03-16 23:08

本文选题：软煤钻孔　切入点：失稳特征　出处：《河南理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：流固耦合作用下的软煤层钻孔失稳破坏原因目前尚无统一的定论。本文通过散体力学、流体力学与固体力学,借助Hoek-Brown强度理论准则,基于数值模拟及实验研究,对软煤钻孔周围失稳破坏情况进行展开分析。探讨了煤层属性对软煤钻孔坍塌压力的影响,分析了在松软煤层中,能形成稳定钻孔半径的范围;随着摩擦角和粘聚力的不断增大,钻孔坍塌的可能性逐渐减小。构建了煤体中包含孔隙的煤粒和裂隙组成的双重结构体,建立煤体双重孔隙钻孔瓦斯双渗流数学模型;基于Hoek-Brown强度理论准则,引入煤体残余抗压强度,修正了耦合公式的不足;建立了流固耦合失稳模型,通过定量GSI的值,运用多物理场软件进行解算,得到如下结论:(1)煤体强度越小,瓦斯对其影响范围越大,其产生的塑性区越大。(2)对于圆形钻孔和椭圆形钻孔,椭圆形钻孔周围卸压松动范围更大,而圆形钻孔更容易产生应力集中现象。(3)偏斜孔周围有效塑性区随着钻孔的钻进,钻孔周围不断扩大,在钻孔底部更容易破坏,而扩容现象更明显。(4)煤体弹性模量动态变化对松软煤层影响巨大,在进行数值模拟计算,分情况探讨。基于打钻过程中煤与瓦斯耦合实验研究,分析了不同瓦斯压力对钻孔周围扰动及变形的影响,实验表明:随着气体压力的增大,钻孔周围出现卸压松动范围越大,同时孔壁变形量也越大。
[Abstract]:At present, there is no unified conclusion on the failure cause of borehole instability in soft coal seams under fluid-solid coupling. This paper is based on numerical simulation and experimental research through bulk mechanics, fluid mechanics and solid mechanics, with the aid of Hoek-Brown strength theory criterion. The instability failure around soft coal boreholes is analyzed. The influence of coal seam attributes on collapse pressure of soft coal boreholes is discussed, and the range of stable drilling radius in soft coal seam is analyzed. With the increasing of friction angle and cohesive force, the possibility of borehole collapse decreases gradually. A dual structure body consisting of coal particles and fractures in coal body is constructed, and a mathematical model of double percolation of gas in coal body with double pores is established. Based on the Hoek-Brown strength theory, this paper introduces the residual compressive strength of coal body and corrects the shortage of coupling formula, establishes the fluid-solid coupling instability model, and calculates it by using multi-physical field software through quantitative GSI. The conclusion is as follows: the smaller the strength of coal body, the greater the influence of gas on it, and the larger the plastic zone is, the larger the loosening range of relief pressure around the elliptical borehole is for circular and elliptical boreholes. The circular borehole is more likely to produce stress concentration phenomenon. (3) the effective plastic zone around the skew hole increases with the drilling, and it is more easily destroyed at the bottom of the borehole. The dynamic change of elastic modulus of coal body has a great influence on soft coal seam. The numerical simulation calculation is carried out and the case is discussed. Based on the experimental study of coal and gas coupling during drilling, the dynamic change of elastic modulus of coal body is more obvious. The influence of different gas pressure on the disturbance and deformation around the borehole is analyzed. The experimental results show that with the increase of the gas pressure, the loosening range of the relief pressure around the borehole is larger, and the deformation of the hole wall is also larger.
【学位授予单位】：河南理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TD712.6

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