Next-Generation Imaging Technique for Underground Object Detection

该项目的目的是开发先进的计算和实验基础，以便利用弹性（即地震）波对地下物体进行方便的3D成像。现有的三维地震分析需要对地下域进行完整的体积离散化，与之相反，该成像技术围绕弹性动力学边界积分方程（BIE）方法，因此只呈现隐藏物体的轮廓。这种仅限边界的传感方法可以节省大量的计算量，它起源于雷达和声纳技术，但在地震勘探的背景下，这种方法在很大程度上尚未得到探索。为了弥补这一差距，本研究的第一阶段侧重于提升原型BIE成像技术，以增加其鲁棒性，考虑更广泛的地下条件，并处理实验和建模错误的有害影响。该项目的实验阶段旨在将新的传感技术应用到一个紧凑的测试装置中，该装置包括一个振动震源和一个三轴运动传感器的表面阵列。研究工作包括：1)综合声学和结构形状优化方面的最新发现，开发快速地面探测技术，从而为高保真BIE成像提供可靠的初始猜测；(2)扩展了噪声污染测量和多层地质矿床处理方法；3)综合计算的发展，为一个强大的，但方便的方法来三维地震传感；4)识别埋在沙箱中的障碍物的方法的小规模实施，以及5)旨在对现有校园地下设施进行成像的现场工作。在上述研究计划的基础上，将继续努力促进在土木工程中越来越多地使用无损检测。新传感技术的潜在应用包括快速探测地下设施和未爆弹药；具有成本效益的城市地区地下基础设施测绘，以及非侵入性的掩埋废物圈定。在这些地区和其他地区，由于电磁测量的分辨率和穿透深度有限，可能不足以进行三维地震成像，因此对快速、经济的三维地震成像的需求尤为明显

The aim of this project is to develop an advanced computational and experimental basis for expedient 3D imaging of subterranean objects using elastic (i.e. seismic) waves. In contrast to existing three-dimensional seismic analyses that require full volume discretization of the underground domain, the proposed imaging technology revolves around an elastodynamic Boundary Integral Equation (BIE) method so that only the outline of a hidden object is rendered. This boundary-only sensing approach, which offers formidable computational savings, has its origins in radar and sonar technologies, but has been largely unexplored in the context of seismic surveys. Aimed at bridging such gap, the first stage of this research is focused on elevating the prototype BIE imaging technique as to increase its robustness, account for a wider class of subterranean conditions, and deal with the detrimental effects of experimental and modeling errors. The experimental phase of this project aims to implement the new sensing technology into a compact testing setup that involves a vibratory seismic source and a surface array of triaxial motion sensors. The research efforts include 1) generalization of the recent findings in acoustics and structural shape optimization to develop a rapid ground-probing technique and thus furnish a reliable initial guess required for the high-fidelity BIE imaging; 2) extensions of the method to deal with noise-polluted measurements and multi-layered geological deposits; 3) synthesis of the computational developments for a robust, yet expedient approach to 3D seismic sensing; 4) small-scale implementation of the method to identify obstacles buried in a sand bin, and 5) a field effort aimed at imaging an existing, on-campus underground facility. The foregoing research program will be complemented with a continuing effort to foster the growing use of non-destructive testing in civil engineering. Potential applications of the new sensing technology include rapid detection of underground facilities and unexploded ordnances; cost-effective mapping of subterranean infrastructure in urban areas, and non-invasive delineation of buried waste. The need for fast and economic 3D seismic imaging in these and other areas is especially pronounced in situations where electromagnetic surveys may be inadequate due to their limited resolution and depth of penetration