Hydraulic properties of clayey soil

[StoyanAndreev]

Hi guys!

Currently I am involved in a benchmark project for the ICOLD (International Committee for Large Dam) for risk assessment of an embankment dam. One of the failure modes is of course sliding instability of the downstream slope. For the project a very simple approach is proposed for the pore-water pressure calculation - from water tables for different pool levels. However I wish to perform some transient seepage analysis to get an insight on how conservative is this approach for the particular case. The organizers don't have hydraulic parameters of the soil, only some strenght properties - friction angle with mean value of 25 degrees and cohesion mean value of 10 kPa (these are effective stress parameters).
My question do you know published relations (if any) between strength properties and hydraulic properties - I need rough estimations of hydraulic conductivity and water content (vs matric suction). Also what value for the hydraulic conductivity anisotropy Ky/Kx is reasonable in your opinion?
Thank you!

 

[fattdad]

I don't have such properties. Just pointing out that the flow net through a dam and the resulting pore pressures along the flow lines are completely independent from permeability.

f-d

ípapß gordo ainÆt no madre flaca!

 

[StoyanAndreev]

Yes, they are independent. But they are dependent on anisotropy in hydraulic conductivity. And in this case study the incoming floods are intense but rather short in duration - about 4h30m so it is conservative to assume steady-state seepage conditions.

 

[killswitchengage]

Hydraulic parameters are not correlated with strength parameters but you can use void ratio and density to assess this problem. Note hydraulic conductivity or permeability is a function of sieve analysis , void ratio, clay mineralogy , density or O.C ratio. One important factor though is that dispersivity is a very tricky question when it comes to clays too