隐藏异质体超宽带多分量探测机理研究

A layered medium with vertical cracks has typical nonhomogeneous or anisotropic properties. Such a medium illuminated by an ultrawideband pulse results in complex electromagnetic scattering phenomena. The detection of cracks and the analysis of geometry in nonhomogeneous media is a challenging task for the application of the GPR to non-destructive detection of engineering quality of transport infrastructure. Essentially,the existing GPR systems use one-dimensional model or scalar scheme to acquire information. The accurate interpretation of raw-data is difficult due to limited acquisition. The proposal develops the ultra-wideband multi-component GPR techniques for detecting the cracked layered heterogeneity in unideal surrounding media (especially in dispersive media). The fluid-filled cracks and fractures may present a high degree of dielectric anisotropy which can be used to explore the GPR vector detection mechanism based on the multicomponent information acquisition. The research contents mainly include these aspects of the multicomponent detection methods for heterogeneity scattering,the high‐resolution spectrum analysis methods for UWB impulse heterogeneity scattering, the multicomponent analysis methods for transient scattered responses,and the reduction methods for the surface reflections and surrounding clutter. After finishing the theoretical analysis and experimental research, it is wished that the obtained results promote efficiently the resolution of the challenge for the detection of hidden cracks in nonhomogeneous or anisotropic media, and thus, provide the key fundamentals to design the advanced nondestructive detection equipments of transport infrastructure.

裂缝性层状体具有典型的非均匀或各向异性媒质特征，在电磁波照射下会产生复杂的传播散射特性，在这样的媒质中探测裂纹或裂缝并研究其几何构造特性是GPR进行道路等工程质量无损探测应用中的难题。现有的GPR技术基本上是以一维地电模型或者是以标量形式获取信息，由于所获得的信息有限，精确数据解释困难。本项目拟开展非理想环境中（尤其是有耗色散媒质）裂缝性层状异质体超宽带多分量GPR探测技术研究，利用裂缝性隐藏异质体非均匀或各向异性的电磁波散射特点，探索GPR探测中多分量信息获取的向量探测机理。主要包括异质体散射回波多分量探测方法研究、异质体超宽带回波信号谱高分辨分析方法研究、异质体超宽带瞬态响应多分量分析方法研究以及表面反射和环境杂波的抑制方法研究。完成有关理论推演和实验研究，期望有效促进典型非均匀或各向异性媒质中裂缝性隐藏异质体探测难题的解决，为我国交通设施等工程质量无损探测先进设备的研制提供技术基础。

主要针对地下裂缝性隐藏目标的几何构造特性的探测问题，开展了目标多极化散射分量和多频率分量分析及其目标探测的应用。主要研究内容包括：地下裂缝目标在水平极化和垂直极化超宽带电磁波照射下的散射传播特性及几何参数估计方法、地埋异质体超宽带散射场瞬态响应特性分析及几何参数估计方法、地埋介电目标冲激响应谐振谱分析及几何参数估计方法、地埋电大尺寸介电目标的扫描机制及几何参数估计方法、GPR发射信号在地电介质传播中的幅度谱和相位特性分析及目标重构方法、超宽带隐藏目标几何形状的高分辨成像方法及复杂环境下地埋目标成像方法等。研究了超宽带电磁脉冲激励下裂缝性目标的散射传播特性，探索了裂缝性目标的极化域特征，建立了三维地下充水裂缝模型，根据极化差在裂缝几何形状上的充分体现，证明能够有效测得地下任意方位裂缝的几何特征，包括走向，长度，宽度及深度，提出了通过不同极化响应分量进行地埋裂缝性目标几何参数估计方法。研究了GPR回波信号在地电介质中的传播特性和地电介质对应的系统函数对超宽带信号的响应特性，构建了相应的数学模型并提出了相应的算法。通过仿真和实验数据验证了所提出方法的有效性。可为实际道路等工程质量探测、提高GPR系统对地埋目标体的定量或者半定量分析提供理论指导。