Multi-length TDR probes: future perspectives

<p>In this contribution we will propose the use of multi-length TDR probes for measurements of the dielectric and possibly magnetic characteristics of a material under test (MUT) as a function of frequency. The multi-length strategy, consisting in making use of a TDR probe with adjustable length of the conductors, can allow the meaningful increase of information achievable about the MUT at each test frequency. We are still at an early stage about these possibilities, and many questions are still open at this time. However, some of our previous studies [1-3] show that the method is promising and can permit the acquisition of some information not intrinsically available from a traditional TDR probe, especially if the MUT shows a dispersive behaviour and possibly magnetic properties. In this contribution, we will discuss the recent work related in particular to geophysical applications.</p><p><strong>Acknowledgements</strong></p><p>This work in progress is being carried out within the European Cost Action CA17115 Mywave.</p><p><strong>References</strong></p><p>[1] R. Persico, M. Pieraccini, Measurement of dielectric and magnetic properties of Materials by means of a TDR probe, Near Surface Geophysics, vol. 16, n.2, pp.1-9, DOI:10.3997/1873-0604.2017046, 2018.</p><p>[2] R. Persico, I. Farhat, L. Farrugia, S. d’Amico, C. Sammut, An innovative use of TDR probes: First numerical validations with a coaxial cable, Journal of Environmental & Engineering Geophysics, doi.org/10.2113/JEEG23.4.437, 23 (4): 437-442, 2018.</p><p>[3] I. Farhat, L. Farrugia, R. Persico, S. D’Amico, and C. Sammut, Preliminary Experimental Measurements of the Dielectric and Magnetic Properties of a Material with a Coaxial TDR Probe in Reflection Mode, Progress In Electromagnetics Research M, Vol. 91, 111–121, 2020.</p>

Methods of engineering geophysics in the control of the reclamation state of agricultural land

The article provides information about the possibility of monitoring the reclamation situation of agricultural land by studying the soil-lithological profile by means of electrometric methods. The essence of the applied resistance method is the study of the soil layer using constant or variable electric fields. For engineering geophysical works in sand-clay sections typical of the Stavropol Territory, various variants of research technologies are presented. The conducted studies have shown the effectiveness of the electrometric method of vertical electrical sounding, which allows, based on surface observations with a minimum amount of control drilling and analytical work, to obtain operational information about changes in the area and depth of such an important parameter for assessing the reclamation state of soils as their specific electrical resistance, depending on humidity and salinity. The VEZ method, in addition to the available information about waterlogged and saline wetlands observed on the earth’s surface by traditional methods, allows us to obtain information about hidden unfavorable zones: about changes in their configuration in area and depth.

A support vector regression approach to predict geotechnical properties of soils from electrical spectra based on Jonscher parameterization

Electrical-conductivity spectra of soils contain valuable information about their texture, structure, and composition that can be linked to their geotechnical properties. Concurrent measurements of electrical spectra in the frequency range of 0.01 Hz to 10 kHz and geotechnical properties, that is, the dry unit weight [Formula: see text], modulus of elasticity [Formula: see text], and the hydraulic conductivity [Formula: see text], are performed on natural soil samples in a laboratory environment. The electrical spectra are modeled with the Jonscher fractal power law model characterized by three parameters: DC conductivity [Formula: see text], transition frequency [Formula: see text], and an exponent [Formula: see text]. We explore a machine-learning technique, the support vector regression (SVR) methodology, to model and predict the geotechnical properties from the Jonscher parameters, and we compare our results with the predictions of multiple linear regression (MLR). For model training and testing, the Jonscher parameters are used as the input, and a geotechnical parameter is used as the output. Model comparisons indicate that the developed SVR models predict [Formula: see text] with an [Formula: see text], predict [Formula: see text] with [Formula: see text], and predict [Formula: see text] with [Formula: see text]. In comparison, MLR models predict [Formula: see text] with an [Formula: see text], [Formula: see text] with [Formula: see text], and [Formula: see text] with [Formula: see text]. The results illustrate that the SVR models are more accurate, reliable, and achieve better performance for predicting the geotechnical properties from the electrical parameters in comparison to the predictions of the MLR models. Our study offers an opportunity in our quest in using noninvasive electrical geophysical methods to obtain geotechnical properties of soils, and it has broad implications in engineering geophysics.