Advanced Analysis of Electromagnetic Waves for Intrinsic Soil Properties

该项目将应用时域反射仪（TDR）信号的时域和频域分析来估计土壤的固有特性，如含水量、密度、电导率、比表面积和宏观土壤。时域反射法是一种被广泛接受的技术，用于岩土工程、地质环境和农业工程应用，具有快速、安全和经济的特点。 在传统的TDR分析中，体积含水量是根据电磁波在土壤探头中的传播时间来确定的，电导率是根据长时间信号的幅度来获得的。 然而，更多关于土壤的固有特性的信息包含在所测量的TDR波形中，这通常不被利用。 利用频率域反演理论可以获得附加信息。 为了实现这一目标，需要精确的模型来描述电磁波在时域反射系统中的传播，并将土壤的固有特性与土壤的电磁特性联系起来。 该方法利用TDR系统的全波形分析结合土壤性质的体积介电混合模型。 这项研究涉及完善和验证正向建模和逆向理论。 本研究的四个主要任务包括：1）提出土壤中电磁波传播的介质混合模型和正演模型; 2）使用改进的介质模型扩展反演理论并进行分辨率和协方差分析; 3）验证正演和反演解; 4）开发实用的鲁棒方法。总的目标是TDR技术成为一个更强大的和实用的工具，用于识别土壤和确定土壤的内在属性。 这项研究的结果也将使TDR一个更有价值的工具，研究基本的土壤行为，包括组成特征，土壤相的体积分数，土-水相互作用，和土壤微观结构。该研究将提高电磁测量的价值，不仅在岩土工程和地质环境工程，而且在农学，土壤科学和农业工程。这项研究的更广泛的影响将通过本科生和研究生的参与，学术界，工业界和政府的测试合作伙伴的继续和扩大参与，为新开发的技术制定ASTM标准，在公开文献中发表，在技术协会会议上发表演讲，以及介绍这些新技术的短期课程。

This project will apply time domain and frequency domain analyses of Time Domain Reflectometry (TDR) signals to estimate intrinsic soil properties such as water content, density, conductivity, specific surface area, and macroscopic soil. Time Domain Reflectometry is a technology widely accepted as fast, safe, and economical for geotechnical, geo-environmental, and agricultural engineering applications. In conventional TDR analysis, volumetric water content is determined from the travel time of the electromagnetic waves in a soil probe, and conductivity is obtained from the amplitude of the signal at long times. However, much more information about the intrinsic properties of the soil is contained in the measured TDR waveforms, which is generally not utilized. The additional information can be obtained by using inversion theory in the frequency-domain. To achieve this goal, accurate models are needed to describe the electromagnetic wave propagation in the TDR system and to relate soil intrinsic properties to the soil electromagnetic properties. The methodology makes use of full waveform analysis of the TDR system combined with a volumetric dielectric mixing model for the soil properties. This research involves refining and validating both forward modeling and inverse theory. The four major tasks of this research include: 1) Advance the dielectric mixing models and forward models for electromagnetic wave propagation in soil; 2) Extend the inversion theory using the refined dielectric models and perform resolution and covariance analysis; 3) Validate the forward and inverse solutions; and 4) Develop a robust methodology for practical use. The overall goal is for the TDR technique to become a more powerful and yet practical tool for identifying soils and determining soil intrinsic properties. Results of this research also will make TDR a more valuable tool for studying fundamental soil behavior including compositional characteristics, volumetric fraction of soil phases, soil-water interaction, and soil microstructure. The research will enhance the value of electromagnetic measurements not only in geotechnical and geo-environmental engineering, but also in agronomy, soil science, and agricultural engineering.Broader impacts of this research will be achieved by the involvement of undergraduate and graduate students, continuation and expansion of participation of testing partners from academia, industry, and government, development of ASTM Standards for the newly developed technologies, publication in the open literature, presentations at technical society meetings, and short courses to introduce these new technologies.