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SWCC Prediction: Seep/W Add-In Functions

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Technical Report

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ERDC-GSL Vicksburg United States

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The soil water characteristic curve SWCC defines a constitutive relationship between the negative pressure that develops when a soils saturation level is less than fully saturated, and the corresponding volume of water held in the pore space of the soil matrix. As this relationship is not commonly measured in geotechnical laboratories, practitioners often attempt to predict this relationship based on other commonly measured material properties using empirical prediction methods. The performance of five SWCC empirical predictors was evaluated through comparisons to independently measured SWCC data for four soils. SWCC prediction methods were selected for this investigation if they incorporated commonly measured soil properties to predict the SWCC. The error in the SWCC prediction was assessed in terms of both the mean squared error on the SWCC prediction and the impact of the error on a numerical analysis of the Green and Ampt infiltration problem. The results of the numerical analysis were assessed in terms of a normalized saturation coefficient. The normalized saturation coefficient provided a clear means of monitoring a transient seepage analysis through a single measure. Results indicate that the SWCC prediction methods yielding the lowest mean squared error did not necessarily yield the smallest error in the transient seepage analysis. Further, only the Rawls method consistently yielded conservative analysis results for all soil types investigated.

Subject Categories:

  • Soil Mechanics

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