Intrinsic Relationship between Specific Surface Area and Soil Water Retention
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Specific surface area (SSA) is a fundamental property of soil. A new methodology for SSA determination of both expansive and nonexpansive soil based on interpretation of the soil water retention curve (SWRC) is proposed and evaluated.

The SWRC-based methodology relies on the Khorshidi-Lu water sorption model, where hydration of expansive soils is interpreted to occur on three distinct surfaces and in sequential order: exchangeable cations, intercrystalline surfaces, and external particle surfaces. Hydration at these different sites is responsible for the commonly observed hysteresis in specific moisture capacity (SMC) between adsorption and desorption paths. Hydration mechanisms for nonexpansive soils, where intercrystalline surfaces do not exist, are shown to be well captured by interpreting the Brunauer-Emmett-Teller (BET) multilayer sorption theory if the effect of cation hydration on the SWRC is considered. A suite of materials ranging from silty to clayey soils is used to demonstrate the validity of the SWRC-based methodology. A comparison of SSA values obtained using the SWRC-based methodology, two existing water-vapor-based methods, and the ethylene glycol monoethyl ether (EGME) method confirms the validity and the accuracy of the SWRC-based methodology. Agreement between SSA values calculated based on the SWRC approach and the EGME method for nonexpansive soils and expansive soils as estimated by root-square-mean error (RSME) is 9m2/g9  m2/g and 80m2/g80  m2/g, respectively. A limitation of the EGME method for the SSA determination of expansive soils is also identified.

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Publication Summary

  • Geosyntec Authors: Morteza Khorshidi
  • All Authors: Morteza Khorshidi, S.M.ASCE; Ning Lu, F.ASCE; Idil Deniz Akin, S.M.ASCE; and William J. Likos, M.ASCE - See more at:
  • Title: Journal of Geotechnical and Geoenvironmental Engineering - See more at:
  • Event or Publication: Publication
  • Practice Areas: Contaminated Sites, Environmental Management, Water and Natural Resources, Water Management
  • Citation: / Volume 143 Issue 1 - January 2017
  • Date: 2016