Evaluating the electrical resistivity of microbial-induced calcite precipitate-treated lateritic soil
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Evaluating the electrical resistivity of microbial‑induced calcite precipitate‑treated lateritic soil J. E. Sani1 · G. Moses1 · F. O. P. Oriola1 Received: 11 May 2020 / Accepted: 29 July 2020 © Springer Nature Switzerland AG 2020
Abstract Organisms or chemicals introduced into soils for soil improvement tend to make such soil reactive and this may affect the parameters that are used to determine the engineering and other properties of the soil. In this study, the electrical resistivity of Bacillus pumilus microbial-induced calcite precipitate-treated lateritic soil at different compactive effort was evaluated; lateritic soil was treated with stepped densities of B. pumilus suspensions of 0/ml, 1.5 × 108/ml, 6.0 × 108/ml, 12 × 108/ml, 18 × 108/ml and 24 × 108/ml, respectively, and compacted with three compaction energies, namely British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy. The treated soil samples were cured for 7, 28 and 56 days to also see the effect of the curing period on the resistivity of the treated lateritic soil. The resistivity test result shows an increase in resistivity value with an increase in B. pumilus suspension density and also with an increase in compactive energy. Though there is a marginal increase between BSL and WAS compactive effort. The peak resistivity value was obtained at 2.4 × 109 cells/ml of B. pumilus suspension density for all compactive effort considered. The effect of curing days indicates that beyond 28 days there is only a marginal increase in resistivity value because there is little or no increase in the resistivity values obtained. Keywords Bacillus pumilus · Electrical resistivity · Compactive effort · Curing days · Lateritic soil
1 Introduction Electrical resistivity of soil is a measure of the resistance that a soil type (of a specified volume) offers to the flow of electricity through it. An estimate of soil resistivity and its variation with depth in the soil is critical in the designing of the grounding system in an electrical substation. It is also needed for designing earthen electrodes for highvoltage direct current transmission systems. The soil resistivity value varies substantially with changes in moisture content, chemical content (salts), temperature, etc. [43]. It is measured in Ohm-meter (Om). The geotechnical community often assumes that natural soil deposits and graded fills are inert due to their ignoring biological presence in soils (that soils are free of organisms) and in a stable state. However, biological
presence can modify the engineering properties of soil greatly [9]. Bio-geochemical processes have been used to improve the engineering properties of soil such as physical properties, conduction properties, mechanical properties and chemical composition and are well documented in the literature [8, 9, 14, 19, 20, 38, 40, 42]. Therefore, it becomes necessary to determine the effect of biological processes on properties of treated soils, most especially those that have found popular use in construction, such as
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