Heterogeneous glacial deposits dominate large parts of the Northern Hemisphere. In these landscapes, high-resolution characterization of the geology is crucial for understanding contaminant transport. Geological information is mostly obtained from multiple boreholes drilled during a site investigation, but such point-based data alone do not always provide the required resolution to map small-scale heterogeneity between boreholes. Crosshole ground penetrating radar (GPR) is suggested as a tool for adding credible geological information between boreholes at contaminated site investigations in industrial sites where infrastructure, such as electrical installations, can pose a challenge to other geophysical methods. GPR data are sensitive to the dielectric permittivity and the bulk electrical conductivity, which can be related to the distribution of water content and sand/clay occurrences. Here we present a detailed crosshole GPR dataset collected at an industrial contaminated site in a clay till setting. The data are processed using a novel inversion approach where information on changes in the velocity and attenuation of the radar signal are obtained independently. The GPR results are compared to borehole logs, grain size analyses, and relative permeability data from the site. The GPR data analysis provided valuable information on the understanding of the lateral geological variability. A silt layer with a thickness of a few decimeters, likely important for flow characterization, was confirmed and resolved by GPR data. Our findings suggest that crosshole GPR has the potential for contributing with high-resolution geological information by filling the data gap between boreholes, thereby becoming a relevant tool in contaminated site investigations.

中文翻译：

---

粘土矿区跨孔探地雷达的高分辨率地质信息

异质冰川沉积物主导着北半球的大部分地区。在这些景观中，高分辨率的地质特征对于了解污染物的迁移至关重要。地质信息主要是从现场调查期间钻取的多个钻孔中获得的，但仅靠这种基于点的数据并不总能提供所需的分辨率来绘制钻孔之间的小尺度异质性。建议将跨孔探地雷达（GPR）作为一种工具，用于在工业场地污染场地调查的钻孔之间添加可靠的地质信息，这些工业场地的基础设施（例如电力装置）可能对其他地球物理方法构成挑战。探地雷达数据对介电常数和体电导率敏感，这可能与含水量的分布和砂/粘土的出现有关。在这里，我们展示了在粘土耕作环境中的工业污染场地收集的详细跨孔探地雷达数据集。使用新颖的反演方法处理数据，独立获得雷达信号速度和衰减的变化信息。将探地雷达结果与现场的钻孔测井、粒度分析和相对渗透率数据进行比较。探地雷达数据分析为了解横向地质变化提供了有价值的信息。探地雷达数据确认并解析了厚度为几分米的淤泥层，这对于流动表征可能很重要。我们的研究结果表明，跨孔探地雷达有潜力通过填补钻孔之间的数据差距来提供高分辨率地质信息，从而成为污染场地调查的相关工具。