Relationship between SWCC and the pore-size distribution fun

A discussion forum for RETC users. RETC is a program which can be used to analyze the soil water retention and hydraulic conductivity functions of unsaturated soils.
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chlgk
Posts: 3
Joined: Wed Jan 20, 2016 12:49 am
Location: Singapore

Relationship between SWCC and the pore-size distribution fun

Post by chlgk » Thu Feb 18, 2016 1:58 am

Hi every one,

I would like to draw your attention on the relationship between the SWCC and pore-size distribution function which we usually used for prediction of the permeability function.
As we known, there are three forms of SWCC including gravimetric water content,w, volumetric water content,sitaw and degree of saturation, S. The question is: which form is most analogous to the pore-size distribution function. It is found that only the SWCC in the form of degree of saturation can be considered analogous to the pore-size distribution function.

The detailed explanation can be found in attached paper.
Zhai Q, Rahardjo H. (2015) “Estimation of permeability function from the Soil-Water Characteristic Curve” Engineering Geology 199: 148-156.

It also illustrates that prediction result on the permeability function from SWCC in the form of gravimetric water content and degree of saturation. Definitely, the predicted result from SWCC in the of degree of saturation is much better than that predicted from SWCC in the form of gravimetric water content as compared with experimental data.

Discussion is welcomed.

Jirka
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Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Relationship between SWCC and the pore-size distribution

Post by Jirka » Thu Feb 18, 2016 2:23 am

Since there is a linear relationship between all these variables (i.e., gravimetric water content, volumetric water content, and degree of saturation), I do not see why one would have significant advantage over the others, other perhaps that degree of saturation goes from zero to one. J.

chlgk
Posts: 3
Joined: Wed Jan 20, 2016 12:49 am
Location: Singapore

Re: Relationship between SWCC and the pore-size distribution

Post by chlgk » Thu Feb 18, 2016 5:41 am

Jirka wrote:Since there is a linear relationship between all these variables (i.e., gravimetric water content, volumetric water content, and degree of saturation), I do not see why one would have significant advantage over the others, other perhaps that degree of saturation goes from zero to one. J.
If ignore the soil volume change, there is a linear relationship. If soil volume change cannot be ignored, then there is no linear relationship any more. Sometimes, the effect of suction on the soil volume change is significant and the soil volume change cannot be ignored.

SWCC in the form of degree of saturation which considers the soil volume change will be different as that ignores the soil volume change.

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