【作者】 于师建；

【导师】 刘家琦；

【作者基本信息】 哈尔滨工业大学 ， 一般力学与力学基础， 2008， 博士

【摘要】 声波和电磁波探测技术在水电、铁路、煤炭、石油及建筑等领域中作为工程地质勘查、岩体工程稳定性研究、工程质量无损检测、工程安全评价等方面的一种重要技术手段发挥了非常重要的作用。实际大型工程地质探测的特殊性要求探测仪器和数据处理方法能够适应大尺度复杂结构体的高分辨率探测。基于此,在声波探测仪器、声波层析成像正反演算法和实际探测应用以及电磁波衰减时频特性方面开展了系统的研究。第1章概述了层析成像的发展历史和常见的几种图像重建算法;重点分析了目前声波、地震波射线追踪算法的发展现状,指出了开展三角网射线追踪研究的意义。针对矿井电磁波透视存在的问题,指出了在频域内开展电磁波衰减特性研究的意义。第2章首先给出了大透距声波探测仪的系统组成、性能指标及大功率超磁声波换能器的结构和特点;其次详细叙述了仪器采集系统的信号采集、显示及信号处理等各项操作功能;最后给出了在顶煤厚度探测和大跨度混凝土结构无损检测中的应用实例。第3章围绕着二维复杂区域的三角剖分,根据剖分区域点、线、面的拓扑关系,遵循Delaunay三角剖分的优化准则实现了适合复杂二维区域特点、地球物理正反演要求的三角网剖分算法,并且在生成节点和网格的同时,考虑了密度控制函数,实现了自适应功能。第4章提出并研究了复杂结构三角网射线追踪全局算法。在第2节定义了三角单元射线追踪的拓扑关系及相关概念;从波前邻域点最小走时计算及相应次级源的选定、波行面扩展和波传播路径的向源检索三个方面论述了节点次级源近似全局算法;实际次级源检索采用了双曲线近似全局算法。在第3节给出了三种不同类型模型的射线追踪结果,并对二水平层介质模型的理论计算结果与数值模拟结果进行了比较。第5章叙述了声波层析成像的基本理论,讨论了基于三角网的射线层析成像图像重建技术。对不规则区域内含有薄板低速子域和圆状低速子域的复杂结构模型进行了层析反演数值模拟,详细给出了7次迭代过程的射线追踪结果和层析反演速度分布结果。数值模拟结果表明,三角网射线层析成像方法具有复杂区域适应性强、速度界面描述灵活、分辨率高、成像结果更接近实际结构形态特征的显著特点。第6章给出了大透距声波层析成像技术在煤层底板破坏深度和大跨度混凝土结构工程质量检测方面的试验研究成果。在第1节介绍了采场底板岩层移动破坏规律及底板破坏的波场响应特征;给出了底板破坏声波层析成像探测的观测方案和探测成果;详细分析了底板岩体声波速度在时间和空间上随工作面推进的动态变化过程,准确地确定了煤层开采后底板破坏带深度。第2节给出了跨度12m的混凝土结构体的纵波和横波速度的层析成像结果。第7章以煤矿采场中存在高电阻率或低电阻率电性地质异常体为实际背景建立物理模型,采用有限差分法对电磁波波动方程进行二维正演数值模拟。根据正演模拟结果,研究了采场电磁波衰减的时频特征,对比分析了场强衰减法层析成像和质心频移法层析成像的效果。在结论部分,对论文工作进行了全面总结,并指出了今后的研究方向。更多还原

【Abstract】 As an important technique applied in engineering geological exploration, the study rock mass engineering stability, non-destructive engineering quality inspection, engineering safety evaluation and other aspects, acoustic wave and electromagnetic wave detecting techniques play important roles in hydroelectricity, railway, coal, petroleum, architectural and other fields. The large-scale engineering geological detecting requires that the acoustic wave detector and data processing method can be adaptable to the high resolution detection of large-scale complex structure mass. Hence, sonic detector, acoustic wave tomography forward and inverse algorithm and their applications, and the attenuation time-frequency character of electromagnetic wave were systematically investigated in the present work.In chapter 1, the general development of tomography and several common image reconstruc-tion algorithms are reviewed. The current status in acoustic wave raytracing algorithms are analyzed. The importance of studying the triangle grid raytracing algorithm is explained. For problems in the coal mine electromagnetic wave penetration, the study on electromagnetic wave attenuation characters in frequency-domain is significant.In chapter 2, firstly, the system components, performance indeies of the large-scale sonic detector and the structure and features of the superpower GMM acoustic transducer are listed. Secondly, functions, like signal collecting, presenting, signal processing are described in detail. Finally, two application exmples in the detection of roof coal thickness of mine working faces and the non-destructive inspection of large span concrete structures are given.In chapter 3, according to the topology relationship of the node, line and face in subdivision area for the triangle subdivision of 2-demension complex structure, triangle subdivision algorithm that meets the characteristic of complex 2-dimensional area and geophysical forward and inversion is realized based on the the optimization rule of Delaunay triangle subdivision. The density control function is considered while the nodes and grid are formed and conformation function by itself is realized.In chapter 4, complex structure triangle grid raytracing global algorithm is put forward and reseached. In section 4.2, the definitions on the topological relations and related ideas of triangle cells raytracing are given. The approximate global algorithm of secondary sources of nodes is discussed in three aspects: calculation of the least travel time of wave front neighborhood points and choosing of their secondary sources, the wave level expansion and the regressive retrieving of wave ray paths. Hyperbola approximate global algorithm is used in the true secondary sources retrieve. In section 4.3, the results of the raytracing for three kinds of models are given. the results of theory calculation and the numerical simulation for the two level stratified model are compared.In chapter 5, the basic theory of acoustic wave tomography is described and the image reconstruction techniques of the ray tomography based on triangle grid are discussed. The tomography inversion numerical simulation on complex structure model of irregularity area with thin slab low speed subfield and circle low speed subfield is performed. The program also gives the raytracing results and the model velocity distributions iterative process of tomography inversion for 7 times. The results of numerical simulation indicate that the triangle grid tomography method has some obvious characteristics, including high adaptability in complex area, flexible description of velocity interface, high resolution, and the imaging results closer to the real structure shape feature.In chapter 6, the results of detection test on the destruction depth in the floor of the coal seam with large-scale acoustic wave tomography and the results on the engineering quality inspection of large span concrete structures are given. In section 6.1, the movement and failure regularity of stratum in the floor of working faces and the wave field response of floor’s failure are introduced. The schemes and the results of acoustic wave tomography for detecting the failure depth in the floor of the coal seam are given. The dynamic changing process about P-wave velocities of floor stratum with the working face impelling is analyzed in detail, and the exact depth of destruction band at the floor of coal seam exploited is determined. In section 6.2, the P-wave and S-wave velocities tomography results of the concrete structure with a span of 12m are obtained.In chapter 7, the physical model is established and the abnormal geological objects with high or low resistivities in the working face are taken as the practical background. Two-dimensional forward numerical simulation for electromagnetic wave equation is implemented with the finite-difference method. According to the simulation results, the time-frequency domain attenuation features are studied respectively. The tomography results of field intensity and centroidal frequency shift are compared.In conclusion, the research work of this dissertation is summarized, and the future developing directions are indicated.更多还原