Dear Alireza,
For the compressibility beta of the air-water mixture you can use the
following form (Bishop
& Eldin 1950, Fredlund & Rahardjo 1993):
beta = 1/Kw = S*betaw + (1-S+h*S)/(pa + po)
where S = degree of saturation; betaw= water compressibility (4.58*10-7
kPa-1); h = volumetric coefficient of air solubility (0.02); pa = air
pressure; po = water pressure; Kw = water bulk modulus. An initial
degree of saturation of 0,95 is reasonable. A discussion about the use
of this formula can you find in our paper Kohler, Feddersen, Schwab
(1999) - "Soil and structure deformations due to reconstruction of an
old lock built on unsaturated submerged clay" presented at the
International Symposium on pre failure behaviour of geomaterials held in
Torino 1999.
sincerely,
Radu
Alireza Bagherieh wrote:
>Dear Colleagues,
>
>I have modeled multi layer construction of an
>embankment dam with an explicit Lagrangian finite
>difference program, I want to model pore pressure
>build up. For this purpose I am using coupled analysis
>in two phase medium. I have a doubt in selecting bulk
>modulus of water. I have used 2*10^8 Pa for this
>parameter. I think this parameter reduces because of
>solution of air in water. Is it logical to reduce bulk
>modulus to 2*10^8 for this reason? What is your
>suggestion for this parameter?
>
>yours,
>A. R Bagherieh
>
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