利用探测雷达探测铁路路基含水率

发布时间：2018-07-06 09:12

本文选题：探地雷达 + 速度分析　；参考：《吉林大学》2017年硕士论文

【摘要】：随着中国经济的快速发展,高铁已经进入我们的生活。在中国的东北和青藏等地区的铁路建设中,冬季的冰冻使得地下含水率较高地段发生冻胀,成为铁路运行速度和安全的重大隐患之一,因此铁路路基含水率的问题不容忽视。探地雷达是一种利用电磁波进行无损探测的浅层地球物理技术,利用探地雷达探测铁路路基含水率是近年来的一个研究热点。本文主要研究内容是实现利用探地雷达准确探测铁路路基含水率,以及证明该方法的有效性和可行性。探地雷达用于近地表含水率探测的研究在国内外已有很多成功的先例。目前,利用探地雷达测量土壤含水率的主要方法有4种:反射波法、钻孔雷达方法、地面波法和反射系数法,其中反射波法为常用方法。共中心点法(Common mid-point简称CMP)是反射波法的一种测量方式,本文应用该方法实现铁路路基原始数据的测量。速度分析原理是对CMP数据提取地层速度信息的主要理论依据。因为铁路路基为水平层状介质,所以利用速度分析获取的叠加速度即为均方根速度。可以利用Dix公式可以将它转换为层速度,从而求得地下介电常数分布。Topp公式表征了介电常数与含水率的关系,进而得到地下含水率,当获取一些列的地下含水率之后通过插值的方式呈现地下含水率剖面图。由于铁路路基每一层的厚度相对雷达信号脉冲宽度较薄,表现为浅薄地层,这为常规速度分析准确提取路基信息带来了很大的难度。为了能够准确的提取铁路路基含水率,本文以实际铁路路基为依据,基于GprMax平台进行数值模拟,分析了不同模型情况下的雷达响应,并对正演结果给出了解释和分析。在分析的过程中发现了来自多次波及折射波干扰的问题,为了解决这一问题提出了最优道集速度分析的方法,该方法能够有效的解决上述问题并准确拾取地层信息。为了能够让最优道集方法适用于更多不同的铁路路基情况,本文通过大量数值模拟并总结出最优角度,它的大小为75度。在速度分析的过程中只要保持反射角小于最优角度,那么就可以减少折射波和多次波对速度分析产生的影响。最优角度适用于不同地层厚度不同介电常数情况下的速度分析。本文进一步分析了天线频率、时间矫正、天线移动步长对准确探测铁路路基含水率的影响。发现高频天线可以消除一部分多次波的影响;时间矫正对速度分析的结果具有很大的影响;天线移动步长对数据的采集提供可靠的依据。极化率法是较为可靠反映含水率异常位置及相对大小的一种方法。利用对模拟数据的处理经验指导实测雷达数据的处理,多个实测数据的处理结果与对应的极化率结果对比发现,两者异常位置基本一致。因此,证明了探地雷达测量铁路路基含水率的方法是有效的、可靠的。并且该方法具有无损伤、分辨率高、低成本的特点,具有一定的推广价值。为了推广这一方法的使用,并且能够让它在实际工作中提高数据处理效率,开发了一套能够快速处理实测数据的软件系统。该软件是基于Matlab的GUI环境完成的,具有快速、高效、准确的处理数据并具有成像的功能。
[Abstract]:With the rapid development of China's economy, the high speed rail has entered our life. In the railway construction in the northeast and Qingzang areas of China, freezing in winter has made frost heave in the high water content area, which has become one of the major hidden dangers for the railway running speed and safety. Therefore, the problem of the water content of the railway subgrade can not be ignored. It is a shallow geophysical technology using electromagnetic wave for nondestructive detection. Using ground penetrating radar to detect the water content of railway subgrade is a research hotspot in recent years. The main content of this paper is to make use of ground penetrating radar to detect the moisture content of railway subgrade accurately, and to prove the effectiveness and feasibility of this method. There are many successful precedents in the study of near surface water content detection at home and abroad. At present, there are 4 main methods to measure soil water content by Ground Penetrating Radar: reflection wave method, drilling radar method, ground wave method and reflection coefficient method, in which the reflection wave method is commonly used. The common center point method (Common mid-point for short CMP) is a reflection wave method. A measuring method is used to measure the original data of the railway subgrade by this method. The principle of velocity analysis is the main theoretical basis for extracting formation velocity information of CMP data. Because the railway subgrade is a horizontal layered medium, the superposition velocity obtained by the velocity analysis is the mean square root speed. The Dix formula can be used to make use of the formula can be used. It is converted into layer velocity, thus the.Topp formula of the subsurface dielectric constant distribution is obtained to characterize the relationship between the dielectric constant and water content, and then the underground water content is obtained. After obtaining some underground water content, the subsurface water cut profile is presented by interpolation. Because the thickness of each layer of the railway base is relative to the radar signal Mai Chongkuan. In order to accurately extract the water content of the railway subgrade, this paper is based on the actual railway subgrade, based on the GprMax platform, and analyzes the radar response under the different model conditions, and gives the forward results. In the process of analysis, the problems from multiple wave and refraction interference are found. In order to solve this problem, an optimal path set velocity analysis method is proposed. This method can effectively solve the above problems and pick up the information of the formation accurately. In order to allow the optimal path set method to be suitable for more different railway subgrade. In the case of a large number of numerical simulations and summing up the optimal angle, its size is 75 degrees. In the process of velocity analysis, the effect of refraction and multiple waves on velocity analysis can be reduced as long as the reflection angle is less than the optimal angle. The optimal angle is applicable to the velocity of different dielectric constant of different thickness. The influence of antenna frequency, time correction and antenna moving step on detecting the water content of railway subgrade is further analyzed. It is found that high frequency antenna can eliminate the influence of a part of multiple waves; time correction has a great influence on the result of velocity analysis; the antenna shift step can provide a reliable basis for data acquisition. The rate method is a more reliable method to reflect the abnormal position and relative size of the water content. Using the experience of processing the simulated data to guide the processing of the measured radar data, the results of the processing of the measured data and the corresponding polarizability results show that the two abnormal positions are basically the same. Therefore, it is proved that the ground penetrating radar is used to measure the railway road. The method of base water content is effective and reliable. And the method has the characteristics of no damage, high resolution and low cost. It has a certain popularization value. In order to promote the use of this method, and can make it improve the efficiency of data processing in actual work, a set of software system which can quickly process the measured data is developed. It is based on Matlab's GUI environment. It has the function of data processing and imaging with fast, high efficiency and accuracy.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U213.1;P631.3

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