Using Resistivity Measurements to Determine Anisotropy in Soil and Weathered Rock (original) (raw)
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Assessment of Soil Homogeneity using Geoelectrical Diametrix in Layered and Weathered Rocks
Zenodo (CERN European Organization for Nuclear Research), 2023
This paper explores the use of diametrically aligned vertical electric sounding VES in assessing homogeneity and anisotropy in layered sedimentary soils and in weathered rock formation. Both Wenner and schlumberger electrode configurations were used in the sedimentary and weathered rock formation respectively, and augmented by geotechnical boring to 30m. The Mann-Whitney U-test was applied to the diametrically aligned VES data where the presence of significant differences between the data sets suggested degrees of uniformity in ground resistivity and by extension compositional quality and structure. Similarly, characteristic values of electrical resistivity in diametrically opposite directions of the geo-layers were determined and compared. By evaluating the differences in apparent resistivity at the same depth, a measure of homogeneity was derived. Various degrees of homogeneity were established at both the sedimentary and weathered formation. I.
Geophysical And Geotechnical Characterization of shallow subsurface soil
Arabian Journal of Geosciences, 2020
The proper design and successful construction of engineered structures require determination of the engineering properties of the soil. These properties, however, are conventionally determined in the laboratory using soil samples collected from the construction site. The collection of soil samples is generally an expensive and time-consuming activity, while the extraction of an undisturbed soil sample is difficult. Furthermore, there are wide variations in the temporal and spatial properties of soil and their accurate evaluation requires high-density sampling. Recently, electric resistivity surveying has attracted much attention. It is commonly applied in the analysis of engineering sites, as it is rapid, cost-effective, and non-destructive. Based on this hypothesis, electrical resistivity was measured at four boreholes in the areas surrounding the University of Peshawar using standard methods of resistivity survey, i.e., Schlumberger electrode configuration. The resistivity data that was obtained by vertical electrical sounding (VES) from the fieldwork was correlated with geotechnical data obtained through the analysis of soil samples in the laboratory. Electrical resistivity had an inverse relationship with gravimetric moisture content and cohesion, with the highest regression coefficients observed in the case of GYM-UAP and Girls' Hostel-UAP (R 2 = 0.97 and 0.96) boreholes, respectively. Moreover, electrical resistivity had a significant linear correlation with the angle of internal friction and standard penetration test-N (SPT-N) values, with the highest regression coefficient of GYM-UAP (R 2 = 0.99) and Girls' Hostel-UAP (R 2 = 0.95), respectively. In conclusion, the obtained relationships between electrical resistivity and different geotechnical properties could be adopted for the assessment of geotechnical properties of soils, especially when many samples are difficult to obtain.
Integrating Geo-Electrical and Geotechnical Data for Soil Characterization
International Journal of Applied Physics and Mathematics, 2012
Precise determination of engineering properties of soil is essential for proper design and successful construction of any structure. The conventional methods for determination of engineering properties are invasive, costly and time-consuming. Electrical resistivity survey is an attractive tool for delineating subsurface properties without soil disturbance. Reliable correlations between electrical resistivity and other soil properties will enable us to characterize the subsurface soil without borehole sampling. This paper presents the preliminary results of an ongoing research on correlations of electrical resistivity with strength properties of soil. Soil investigations, field electrical resistivity survey (VES) and laboratory electrical resistivity measurements were conducted. From the data analysis, significant correlations have been obtained between resistivity and moisture content and angle of internal friction. Weaker correlations have been observed for cohesion and unit weight of soil.
The Open Civil Engineering Journal
Background: Electrical resistivity tests at a project site could be a valuable economical alternative to typical geotechnical soil exploration and a reliable source of data. In the present study, the soil at a constructed underground water tank site in Qassim Region – Saudi Arabia is investigated using the electrical resistivity testing method. Objective: The study aims to compare the results of traditional soil boreholes that were conducted at various stages of the project lifetime with the interpretation of soil resistivity test results. Methods: Eight soil boreholes were drilled at the water tank site to capture the nature of soil layers. The electrical resistivity of soil layers at the site is measured and used to investigate the ground subsurface of the project site. The geophysical software, ZondRes2d is utilized to analyze and interpret the collected data. Results: Both geotechnical soil boreholes and geophysical electrical resistivity tests revealed similar soil profiles wit...
Predicting sandy-clayey soil properties using electrical resistivity testing
Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, 2019
Non-destructive tests are economical and easy-to-use techniques to determine different soil properties, which speed up the determination of sub-surface characteristics. They include ground-penetrating radar, seismographs, shear wave velocity and electrical resistivity testing. The latter is gaining worldwide popularity for determining sub-surface geology in geotechnical engineering as it does not require extensive testing. The aim of the study reported in this paper was to develop empirical correlations of electrical resistivity testing with different soil parameters by performing extensive conventional laboratory tests. These correlations would help in computing the required soil parameters by performing solely electrical resistivity testing, saving the time and effort required by conventional tests. The correlations developed included the relationship of resistivity values of soil with the drained angle of internal friction, effective cohesion, Atterberg's limits, maximum dry ...
2010
The detection of contamination plumes is extremely important, since they may represent serious risks for the population and the environment of a given region. The resistivity piezocone (RCPTU), as Campanella & Weemees (1990) and Campanella & Kokan (1993) suggestions, is a relatively recent technological development of the piezocone, in which a resistivity module is installed at the back of a standard piezocone. This resource enables continuous measurements to be taken of the resistance to an electric current applied to the ground. When measured in the ground in a series of tests, this current flow allows for the detection of the probable presence of certain substances by means of comparison against reference values. These reference values are established based on field work or on similar geological environments. However, the values reported in the literature refer to typical soils of temperate climates and do not reflect the behavior of tropical soils. To allow for a study of refere...
Acta Geophysica, 2020
Sundry soils/rocks are characterized by electrical properties with clearly or obscurely expressed anisotropies. These anisotropic effects may be low, moderate or high depending on the coefficient of anisotropy (λ). The vertical electrical sounding technique employing Schlumberger electrode configuration and lithological information from boreholes were deployed to characterize the lithological diversity in homogeneous and anisotropic geologic units that serve as aquifer systems and their overlaying layers in the coastal region of Akwa Ibom State. Based on the , the assessed volume of sedimentary formation is classified into low anisotropy λ < 1.2, moderate anisotropy (1.2 < ≤ 1.3) and high anisotropy (> 1.3) with alluvium (64.3%), inter-bedded shale and sandstone (14.3%) and shale and slate (21.3%). The estimated percentage of respective compositional coverage indicates that alluvium is dominant, while the blended inter-bedded shale and sandstone as well as the shale and slate are minor geologic units in the Benin Formation. Inferred index of spread of alluvium indicates that the homogeneous and anisotropic units assessed are intrinsic/microscopic in nature as identified by the impressed current that passed through geologic system. The results showcased that the plot between the strike-dependent resistivity at arbitrary chosen strike and geometric mean resistivity m can be used as a yardstick for inferring the degree of consistency of geologic compositions in homogeneous and anisotropic media. Both the quantitative (graphic) and qualitative (contour) results portend the thin possibility of having anisotropy free geologic units. The finding proposes that ground resistivity measurements and interpretations of geologic structures should be constrained by borehole information in order to firm up the intended plans for obtaining clearer, defendable and well-resolved subsurface structures.
Field Measurement of Hydraulic Conductivity of Rocks
Hydraulic Conductivity - Issues, Determination and Applications, 2011
Hydraulic Conductivity-Issues, Determination and Applications 286 installation. Reynolds et al. (2002) conducted infiltrometer tests under different conditions, Ledds-Harrison & Youngs (1994) used very small diameter rings (from 1.45 mm to 2.5 mm) for field measurements on individual soil aggregates, Youngs et al. (1996) used a 20 m diameter infiltrometer cylinder to measure highly structured and variable materials that could not be sampled adequately by a smaller cylinder. Castiglione et al. (2005) developed in the laboratory a tension infiltrometer ring, 4 cm in height and 27.5 cm in diameter, suitable for accurate measurements of infiltration into a big sample of fractured volcanic tuff, at very low flow rates over long equilibration times. Most field studies employ cylinder infiltrometers with diameters ranging commonly from 1 to 50 cm, which are poorly representative of the heterogeneous media, such as fractured rocks, in which hydraulically important fractures may, typically, be spaced further apart than the cylinder's diameter. Indeed, up to now infiltrometer tests have rarely been performed directly on-site on rock outcrops. This chapter describes a methodology to obtain the field-saturated hydraulic conductivity, Kfs, by using a ring infiltrometer, with a large (~2 m) adjustable diameter, developed for measuring quasi-steady infiltration rates on outcropped rock. Kfs is the hydraulic conductivity of the medium (soil or rock) when it has been brought to a nearsaturated state by water applied abundantly at the land surface, typically by processes such as ponded infiltration, copious rainfall or irrigation. The proposed device is inexpensive and simple to implement, as well as very versatile, owing to its large adjustable diameter that can be fixed on-site. Moreover, certain practical problems, related to the installation of the cylindrical ring on the rock surface, were solved in order to achieve a continuous and impermeable joint surface between the rock and the ring wall. An issue of major concern is linked to the edge effects, related to the radial spreading of the infiltrating water; obviously smaller rings are more influenced by these effects. Swartzendruber & Olson (1961) and Lai & Ren (2007) found that the ring infiltrometer needs a diameter greater than 1.2 m and 0.8 m, respectively, to avoid the edge effects. For this reason, the proposed large ring infiltrometer is made of a strip of flexible material with which build the cylinder on-site, with a suitable diameter in relation to the lithological and topographical features of the field. The flexible material, such as plastic or glass resin, allows the minimization of the size of the ring and, therefore, its movement easily, in order to acquire a large number of independent K fs measurements over a given area. In fact, because of the extreme spatial variability of K fs , its value finds statistical consistency in multiple tests. Geophysical techniques were coupled with the infiltrometer tests in order to monitor, qualitatively, the water infiltration depth, to allow a rapid visualization of the change in water content in subsurface and to ensure that the decrease in the water level in the ring was caused mainly by vertical water infiltration, and not by the lateral diversion of water flow. Since the late 1980s, many geophysical applications have been aimed at hydrogeological studies. White (1988) conducted electrical prospecting to determine the direction and the flow rate of saline aquifers using a tracer. Daily et al. (1992) used borehole electrical resistivity surveys to obtain the distribution of electrical resistivity in the subsurface, and compare the results with infiltrometer tests. Recently, electrical resistivity techniques have been used to monitor hydrogeological processes. Cassiani et al. (2006) conducted a monitoring test of a salt tracer by means of the application of electrical resistivity tomography using a time-lapse technique. The movement of the tracer was monitored with geophysical images. The methodology described in this chapter was carried out on different lithotypes in order to verify the applicability of the experimental apparatus in very different geological conditions. In particular two cases are described: the Altamura test site that represents a case of hard sedimentary rock consisting
Applied Sciences, 2020
Standard test methods may not be suitable or sufficient for determining the geotechnical conditions of a structure’s subsoil and the effects of the designed structures on the environment. Geophysical test methods, validated with other methods, may prove useful. In recent years they have found many new applications in engineering practice, both geotechnical and environmental. The advantages of geophysical methods include the non-destructive and non-invasive nature of the tests, their low costs and quick results, as well as compatibility with different materials, including soils, solid rocks, wastes and anthropogenic formations. The paper presents the analysis of laboratory and field investigations including research in a modified oedometer, resistivity chamber, electrical resistivity tomography (ERT) and resistivity cone penetration test (RCPT). Laboratory tests allowed for the assessment of the degree of saturation and porosity of sandy and clayey soils. The tests were carried out o...