“三软”煤层采动裂隙场与瓦斯流场研究

发布时间：2018-04-02 16:12

本文选题：“三软”煤层　切入点：物理相似模拟　出处：《西安科技大学》2017年硕士论文

【摘要】：随着机械化采掘工艺的推广应用,在高效的现代综合机械化采煤工艺在提高产量和推进速度的同时,矿井瓦斯涌出严重制约了矿井高产、快速采煤,很大程度上制约了我国煤炭工业的发展。为解决“三软”煤层工程背景下采场瓦斯涌出,研究“三软”煤层采动裂隙场、瓦斯流动场规律,是卸压瓦斯治理充足的理论依据。本文通过对主采煤层瓦斯基础参数进行了测定,煤层瓦斯流量衰减系数为β=0.2269296,远大于难以抽放临界值0.05(0.003～0.05 d-1),试验矿井5#煤层属瓦斯难抽放煤层;试验工作面煤层瓦斯放散初速度在7.05～11.0之间,临界值10.0在此区间之内;煤体孔隙率为11.63;煤层坚固性系数为0.5411;煤层平均瓦斯含量为3.0678 m3/t,采用分源预测法预测得工作面相对瓦斯涌出量为2.288 m3/t,工作面按日产量按7000 t/d计算,则工作面绝对瓦斯涌出量为11.122 m3/min。采用物理相似模拟实验和UDEC数值模拟,分析了煤层开采后采场覆岩破断规律、裂隙产生的发展、时空演化规律和分布形态以及卸压范围与特征。采场岩石垮落结果及岩层垮落位移云图表明:工作面周期来压平均步距为8 m,在工作面采场发生第七次周期来压后,主关键层破断,裂隙闭合,地表下沉形成盆地,采空区被逐渐完全压实,采空区覆岩在采动过程中基本趋于稳定状态。距离煤层底板17～29m破断穿层裂隙较为发育,离层裂隙范围在110 m以下,在95～110m范围内,形成离层的覆岩仅发生弯曲下沉,未发生断裂破坏。工作面冒落带最大高度为8～16m,裂隙带高度为45～65 m,冒落带区域内岩体块状破碎充分,穿层裂隙发育。根据工程概况,结合物理相似模拟实验和UDEC数值模拟结果,在模型假设基础上建立了基于覆岩运移规律的三维梯形ANSYS FLUENT物理模型,通过对模型边界条件进行设定,对采场不采取任何措施时进行数值运算,采场最大瓦斯浓度达到53.10%。通过对高位钻孔直径分别0.073 m、0.089 m、0.094m、0.113 m和0.153 m时,结合不同高位抽采直径下采场最大瓦斯浓度与钻孔直径关系图可以看出图中采场瓦斯最大浓度与钻孔直径基本呈负相关,相关系数为0.9115。在钻孔直径为0.153 m时,通过对高位钻孔抽采负压分别为10kpa、15kpa、20kpa、25kpa和30kpa时,采场瓦斯运移进行数值解算,当抽采负压为30 kpa时,采场最大瓦斯浓度为14.06%,从云图中可以看出瓦斯抽采效果非常显著,上隅角处瓦斯明显处于控制之中。工作面现场回风巷已布置高位钻场12个,高位钻孔72个,累计施工钻孔进尺为4860 m,抽放管道内瓦斯浓度为2%～42%,抽放瓦斯纯量为1.29～9m3/min,卸压瓦斯抽采总量为45.82万m3,有效地降低了工作面回采期间瓦斯浓度,说明了卸压瓦斯高位钻孔抽采参数较为合理,达到了预期的效果,为工作面安全生产提供了保证,同时也验证了研究方法的科学性和研究结论的正确性。
[Abstract]:With the popularization and application of mechanized mining technology, the high efficient modern comprehensive mechanized coal mining technology not only increases the output and the speed of propulsion, but also restricts the mine gas emission seriously, which restricts the high yield and fast mining of coal.To a large extent, restricted the development of China's coal industry.In order to solve the problem of gas emission in stope under the background of "three soft" coal seam engineering, it is theoretical basis to study the law of gas flow field in mining crack field and gas flow field of "three soft" coal seam.In this paper, the gas basic parameters of main coal seam are measured. The attenuation coefficient of gas flow in coal seam is 尾 _ (0.2269296), which is far larger than the critical value of 0.05 ~ 0.003 ~ (0.05) d ~ (-1) in difficult drainage. The coal seam in test mine belongs to difficult to drain coal seam.The initial velocity of coal seam gas emission is between 7.05 and 11.0, and the critical value is 10.0.The porosity of coal body is 11.63, the coefficient of coal seam firmness is 0.5411, the average gas content of coal seam is 3.0678 m3 / t, the relative gas emission of working face is 2.288 m3 / t, calculated by daily output of 7000 t / d, the absolute gas emission of working face is 11.122 m3 / min.By using the physical similarity simulation experiment and UDEC numerical simulation, this paper analyzes the overburden rock fracture law, the development of fracture, the space-time evolution law and distribution form, and the pressure relief range and characteristics after coal seam mining.The result of stope rock collapse and the cloud map of rock collapse displacement show that the average step distance of working face periodic pressure is 8 m. After the seventh periodic pressure occurs in the working face, the main key layer breaks down, the fissure closes, and the surface subsidence forms a basin.The goaf is gradually compacted completely, and the overburden of the goaf tends to be stable in the process of mining.The fracture of breaking through layer of 1729 m in distance coal seam floor is relatively developed, the fracture range of separated layer is less than 110 m, in the range of 95 ~ 110m, the overburden that formed the separated layer only bends and sinks, but does not have fracture damage.The maximum height of the caving zone is 816 m and the height of the fracture zone is 45 ~ 65 m. The rock mass in the caving zone is well broken and the fracture in the stratum is developed.According to the general situation of engineering, combined with the results of physical similarity simulation experiment and UDEC numerical simulation, a three-dimensional trapezoidal ANSYS FLUENT physical model based on overburden migration law is established on the basis of model hypothesis. The boundary conditions of the model are set up.The maximum gas concentration of the stope is 53.10 when no measures are taken.The correlation coefficient is 0.9115.When the diameter of the borehole is 0.153 m, the gas migration in the stope is calculated numerically when the negative pressure of the high borehole is 10 kpa-15kpa-20kpa-25kpa and 30kpa, respectively, and the negative pressure is 30 kpa.The maximum gas concentration in the stope is 14.06. It can be seen from the cloud map that the effect of gas drainage is very remarkable and the gas in the upper corner is obviously under control.There are 12 high drilling fields and 72 high drilling holes in the return air roadways in the working face.It is shown that the parameters of high pressure relief gas drilling are reasonable and the expected effect is achieved, which provides a guarantee for the safe production of the working face. At the same time, it also verifies the scientific nature of the research method and the correctness of the research conclusion.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712

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