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Geophysical investigation techniques: electrical
Published in Ian Acworth, Investigating Groundwater, 2019
The most widely used relationship to determine porosity from electrical measurements is Archie’s Law. This has been developed in the oil industry where it was used to predict porosity (and therefore oil content) from the ratio of the fluid resistivity and the bulk resistivity: σb=aσwϕmwhere:σb is the observed electrical conductivity at the surface,σw is the conductivity of the water present,ϕ is the porosity,m is a factor related to grain shape, anda is a constant. Archie’s Law does not work well for fluid conductivities of less than 100 mS/m2, for sediments containing clay, or for partially saturated sediments. Modifications have been suggested to extend the relationship as shown in Equation 9.6: σb=aσwϕmSn+σswhere:σb is the observed electrical conductivity at the surface,σw is the fluid conductivity of the water present,σs is the conductivity associated with the movement of surface charge along clay surfaces,ϕ is the porosity, andS is the saturation.
Relating unsaturated electrical and hydraulic conductivity of cement-based materials
Published in Australian Journal of Civil Engineering, 2018
Quantitative expression of hydraulic and electrical conductivity in terms of saturation and porosity usually requires experimentally-measured or calibrated parameters. In estimating the electrical conductivity of cement-based materials, Archie’s law-based models are popular due to their simplicity (Sant, Bentz, and Weiss 2011). Archie’s law relates σb to the electrical conductivity of the pore solution σp and φ. Archie’s law is written as
Influence of salt content on clay electro-dewatering with copper and stainless steel anodes
Published in Drying Technology, 2019
Zhijia Xue, Xiaowei Tang, Qing Yang, Zhifeng Tian, Yao Zhang
The saturated clay sample includes solid material and pore water. Archie’s law assumes that the conductivity of clay comes from the pore water. The electrical resistivity can be expressed as shown in the following equation: where ρwis the conductivity of the pore water, and a and m are empirical coefficients from the experimental data.[38]