• A new approach in calculating porosity of shallow unconsolidated soil based on Archie’s Law

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    • Keywords


      Porosity; Waxman–Smits equation; normalization; resistivity method

    • Abstract


      Porosity ($\phi$) of soil/rock is frequently approximated using Archie’s Law where bulk resistivity ($\rho_{\rm{o}}$) is obtained from resistivity method while pore-fluid resistivity ($\rho_{\rm{w}}$) relies on well/borehole availability. This research proposes a new approach in obtaining $\phi$ of unconsolidated soil. The study was conducted at Balik Pulau, Minden and Teluk Kumbar. Clay’s presence was determined via particle size distribution (PSD) analysis. PSD graphs’ curves show that Balik Pulau is composed of elastic silt, while the other two sites consist of sand dominantly. For verification, soil samples’ porosities, $\phi_{\rm{sample}}$, were measured to produce 31.93, 32.95 and 26.47% values for the three sites, respectively. The new approach uses saturated layer’s resistivity values for porosity calculation, $\phi_{\rm{resistivity}}$. The resistivity values generated $F_{\rm{a}}$, $\rho_{\rm{w}}$ and $\rho_{\rm{o}}$ with constraints applied according to published reports for the parameters’ range of values. Conventional and normalized Waxman–Smits models were then employed for $\phi_{\rm{resistivity}}$. Conventional model produced $\phi_{\rm{resistivity}}$ of 12.66, 25.33 and 12.94%, while normalized model produced better $\phi_{\rm{resistivity}}$ values of 30.38, 31.91 and 27.32% for the three sites, respectively. Normalized model significantly outperforms with errors of <5%. Hence, the new approach accurately estimates saturated layer’s $\phi$ with no dependency on physical samplings and is applicable even in clay’s presence.

    • Author Affiliations



      1. School of Physics, Universiti Sains Malaysia, Minden, Pulau Pinang, Malaysia.
    • Dates

  • Journal of Earth System Science | News

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      Posted on July 25, 2019

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