Applications of ground penetrating radar in geotechnical investigation

There are clearly risks and a fair degree of uncertainties involved in geotechnical investigation for the reason that only limited boreholes can be used in projects, due to budget restraints. These risks are further increased or decreased subject to the geotechnical engineers’ experiences and judgments. Ground Penetrating Radar (GPR) is a geophysical technique that provides continuous non-destructive soil profiling from the surface or from inside a borehole by sending, receiving and averaging multiple radio wave pulses into the subsurface at centimeter increments (cm) scale normally ranging between 0.5cm to 1cm step size. This project focuses on the principles, procedures, applications and limitations of GPR use in geotechnical exploration. To evaluate its potentials for reducing risk and uncertainties associated with soil profile presumptions between boreholes, also to evaluate if GPR can provide objective quantifiable data that can be understood by any level of geotechnical engineers.

Applications of ground penetrating radar in geotechnical investigation

There are clearly risks and a fair degree of uncertainties involved in geotechnical investigation for the reason that only limited boreholes can be used in projects, due to budget restraints. These risks are further increased or decreased subject to the geotechnical engineers’ experiences and judgments. Ground Penetrating Radar (GPR) is a geophysical technique that provides continuous non-destructive soil profiling from the surface or from inside a borehole by sending, receiving and averaging multiple radio wave pulses into the subsurface at centimeter increments (cm) scale normally ranging between 0.5cm to 1cm step size. This project focuses on the principles, procedures, applications and limitations of GPR use in geotechnical exploration. To evaluate its potentials for reducing risk and uncertainties associated with soil profile presumptions between boreholes, also to evaluate if GPR can provide objective quantifiable data that can be understood by any level of geotechnical engineers.

GPR imaging of traffic compaction effects on soil structures

Spatial and depth variability of soil characteristics greatly influence its optimum utilization and management. Concealing nature of soil subsurface horizons has made the traditional soil investigations which rely on point information less reliable. In this study, an alternative use of ground penetrating radar (GPR)—a near-surface geophysical survey method—was tested to address the shortcomings. The focus of the study was on assessment of characteristics variability of soil layers at a test site and evaluation of effects of compaction caused by machinery traffics on soil. GPR methods utilize electromagnetic energy in the frequency range of 10 MHz and 3.0 GHz. Fourteen profiles GPR data were acquired at the test site-a farmland in Krakow, Poland. Compaction on parts of the soil was induced using tractor movements (simulating traffic effects) at different passes. Data were processed using basic filtering algorithms and attributes computations executed in Reflexw software. Attempt made in the study was on use of GPR geophysical technique for soil assessment. The method allows delineation of the soil horizons which depicts characteristic depth changes and spatial variability within the horizons. Moreover, traffic effects that caused compaction on parts of the soil horizons were discernable from the GPR profile sections. Thus, similar densification like hardpan that may develop in natural setting can be investigated using the method. The results have shown the suitability of the method for quick, noninvasive and continuous soil investigation that may also allow assessment of temporal soil changes via repeated measurement.

Vertical Electrical Sounding (VES) for Estimation of Hydraulic Parameters in the Porous Aquifer

Similarities in both water and electric current flows allow the relation of hydraulic and geoelectric parameters of porous aquifers. Based on this assumption and the importance of the hydraulic parameters for groundwater analyses, this study aimed to estimate hydraulic conductivity (K) and transmissivity (T) with vertical electrical sounding (VES) in the porous aquifer at the experimental farm of the University of Brasilia, Brazil. VES is a geophysical technique that provides electrical resistivity (ρ, Ω m) and thickness (h) of the subsurface layers. The ρ and h aquifer data, associated with lithology, water table level (WTL), and groundwater electrical resistivity (ρw, Ω m), allowed the calculation of complementary geoelectric parameters (formation factor, F, and Dar Zarrouk parameters) and the relation with K and T, determined via slug test. VES data allowed the elaboration of geoelectric models, with mean absolute percentage error (MAPE) below 6% compared to field data, and the identification of the aquifer in each VES station. Significant exponential regression models (R2 > 0.5 and p-value < 0.05) showed the possibility of using geoelectric parameters to estimate hydraulic parameters. This study allowed the verification of the applicability of consolidated models and the identification of appropriate empirical relationships for hydrogeological characterization in the Brazilian tropical porous aquifers. The results of this work, besides the rapid sampling and low cost of performing vertical electrical sounding (VES), may justify the use of this geophysical technique for preliminary porous aquifer characterization, especially in regions absent of or with insufficient monitoring wells.

GEOPHYSICAL INVESTIGATION OF POTENTIAL FELDSPAR DEPOSITS IN MOKWA, NIGERIA FOR ECONOMIC BENEFITS

The geophysical technique of Electrical Resistivity in mineral rocks investigation has been found to be one of the very effective and convenient methods. It was therefore applied using Schlumberger configuration to investigate the location, depth and the economic viability of Feldspar mineral deposits at the study location in Mokwa, Niger State, Nigeria. This research is aimed at determining the location and economic viability of Feldspar deposits in Mokwa that can serve as Industrial fillers or induce the development and sustainability of both small and medium scale paint, plastic, rubber and adhesive Industries within and outside the study area. 30 Vertical Electrical Soundings (VES) were acquired in 6 profiles using ABEM SAS 4000 Terrameter with 50 m spacing in between each profiles. The results revealed that Profile 1 VES point 5, profile 2 VES point 2, profile 4 VES point 4 and profile 5 VES point 5 are underlined with rocks of Low electrical resistivity values which implied possible Feldspar deposits. The highest Feldspar Deposits with average thickness of 7.87 m was discovered in profile 1, while profile 4 exhibited the lowest deposits with thickness of 2.50 m. On the average, the depths of these minerals rocks from the surface fell in the interval of 0.06 m to 8.00 m. However, the discovered feldspar deposits are not of much economically viable for Industrial filler exploration capable of influencing any Industrial development in either small or medium scale capacity.