煤矿复杂采空区瞬变电磁响应及解释方法研究

发布时间：2019-03-02 21:50

【摘要】：我国的能源结构决定了其对煤炭资源的依赖性。随着煤矿开采范围和开采深度的不断增加,所留下的采空区常有大量的积水,极易造成突水灾害。为了避免此类安全事故的发生,寻求探查此类复杂采空区精确位置及富水性的方法具有重要意义。目前,探查煤矿灾害水源的矿井地球物理方法主要有矿井直流电阻率法和矿井瞬变电磁法,其中矿井瞬变电磁法以其施工便捷、工作效率高和对低阻体反映灵敏等特点被广泛应用于煤矿灾害水源的探查。本文通过对煤系地层中发育的单层低阻采空区、高阻采空区及多层采空区等不同地电模型的瞬变电磁物理模拟实验和正演数值模拟计算,分析了不同条件下的复杂采空区的瞬变电磁响应特征。由实验和数值模拟结果可知,高阻围岩中的单层低阻(积水)采空区情况下,瞬变电磁法信号反应灵敏;而高阻(充气)单层采空区情况下,信号反应不灵敏,且探测采空区位置准确性还存在一定误差;多层采空区情况下,两煤层中间层厚度大小与其感应电动势大小成正比关系,并通过数值模拟方法研究了上组煤层和下组煤层在含水及不含水等多种复杂情况下瞬变电磁响应特征。对多层采空复杂区响应结果分析可知,复杂采空区存在的情况下,会对瞬变电磁法探测的分辨率造成不利影响,减弱瞬变电磁法的探测能力。为了克服这种不利影响,须对瞬变电磁解释方法进行针对性改进。基于上述原因在数据解释的同时需要提出一种新的算法消除复杂采空区对瞬变电磁精度的影响。针对复杂煤层采空区的屏蔽影响,本文提出了改进阻尼最小二乘法反演方法完成了瞬变电磁数据拟合。具体研究内容如下:在利用“烟圈”成像反演得出的电阻率剖面作为阻尼最小二乘反演初始模型的基础上,对实测数据进行晚期视电阻率转化,以晚期视电阻率相对误差作为收敛标准,推导了迭代方程,实现瞬变电磁数据拟合,并提出了阻尼因子修正方法、设定了参数上、下界,在保证收敛良好的情况下,完成了阻尼最小二乘法拟合,使迭代参数达到最大步长,提度和精度高了反演算法的运算速。通过对复杂采空区的的正反演理论的研究,结合煤层复杂采空区探测实例,证明所得结论正确性。验证了改进阻尼最小二乘法拟合的实用性与精确性。进一步表明瞬变电磁法对煤矿复杂采空区的探测具有良好的效果。
[Abstract]:China's energy structure determines its dependence on coal resources. With the increasing mining scope and depth of coal mine, there is often a large amount of water in goaf, which is easy to cause water inrush disaster. In order to avoid the occurrence of such safety accidents, it is of great significance to find out the exact location and water-rich property of this kind of complex goaf. At present, the main geophysical methods to explore the water source of coal mine disasters are the mine DC resistance method and the mine transient electromagnetic method, in which the mine transient electromagnetic method is convenient for its construction. The characteristics of high working efficiency and sensitivity to low resistance are widely used in the exploration of coal mine disaster water sources. In this paper, the transient electromagnetic physical simulation experiment and forward numerical simulation of different geoelectric models, such as single layer low resistivity goaf, high resistivity goaf and multi-layer goaf, developed in coal measure strata, are carried out. The transient electromagnetic response characteristics of complex goaf under different conditions are analyzed. The results of experiment and numerical simulation show that the transient electromagnetic method is sensitive to the single-layer and low-resistivity goaf in the surrounding rock with high resistance. In the case of high resistance (inflatable) single-layer goaf, the signal response is not sensitive, and there is some error in detecting the accuracy of goaf position. In the case of multi-layer goaf, the thickness of the middle layer of the two coal layers is proportional to the size of the induction electromotive force (EMF). Through numerical simulation, the transient electromagnetic response characteristics of upper and lower coal seams are studied under various complicated conditions, such as water-bearing and non-water-bearing. By analyzing the response results of multi-layer goaf complex area, it can be seen that the presence of complex goaf will adversely affect the detection resolution of transient electromagnetic method, and weaken the detection ability of transient electromagnetic method. In order to overcome this adverse effect, the method of transient electromagnetic interpretation must be improved. Based on the above-mentioned reasons, a new algorithm is proposed to eliminate the influence of complex goaf on the transient electromagnetic accuracy while interpreting the data. In view of the shielding effect of goaf in complex coal seam, this paper presents an improved damping least squares inversion method to complete transient electromagnetic data fitting. The specific research contents are as follows: based on the initial model of damping least squares inversion, the resistivity profile obtained from smoke ring imaging inversion is used to transform the measured data into late apparent resistivity. Taking the relative error of late apparent resistivity as the convergence criterion, the iterative equation is derived to fit the transient electromagnetic data, and the correction method of damping factor is put forward. The upper and lower bounds of the parameters are set. Under the condition of good convergence, the upper and lower bounds of the parameters are set. The damping least square fitting is completed, and the iterative parameters reach the maximum step size, and the lifting degree and precision are higher than that of the inversion algorithm. Through the study of the theory of forward and inversion of complex goaf and combined with the detection example of complex goaf in coal seam, the conclusion is proved to be correct. The practicability and accuracy of the improved damping least squares fitting are verified. It is further shown that the transient electromagnetic method has a good effect on the detection of complex goaf in coal mine.
【学位授予单位】：河南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P631.325;TD325.3

【相似文献】