Earth Pressure Coefficients for Stiff Clays
Earth Pressure Coefficients for Stiff Clays
(OP)
I'm designing a retaining wall that's roughly 18 foot high. It bears into a stiff to very stiff clay with a coefficient of friction of 0.35 and a bearing pressure of 2500 psf. The unit weight of the soil is roughly 90 pcf. I'm having a difficult time getting a sliding check to work and I'm currently assuming the clay is "ideal" and that it doesn't have any friction associated with it. However, this is making the wall design very difficult. It would help if I were able to assign an angle of internal friction to the clay and apply that to the active and passive pressures to help balance out the forces. Any input on an internal friction value for a stiff clay?






RE: Earth Pressure Coefficients for Stiff Clays
RE: Earth Pressure Coefficients for Stiff Clays
RE: Earth Pressure Coefficients for Stiff Clays
All the parameters should be consistent and this is where an experienced soils report will come in handy. Since you have cohesive soils, you can combine friction, passive and cohesion for calculating sliding stability.
http://www.soilstructure.com/
RE: Earth Pressure Coefficients for Stiff Clays
www.PeirceEngineering.com
RE: Earth Pressure Coefficients for Stiff Clays
FixedEarth - The navy manual that was provided gives the following information for CH soils: friction angle = 19 degrees, Unit weight = 75-105 lb/ft3. I'm going to go with the sliding friction coefficient of 0.35 and the bearing capacity of 2500 psf (although it may be quite conservative as you indicate) because those are the only two values that the geotechnical report actually specificed (unfortunately!
I guess I was just confused because there was a lot of talk about not applying a friction angle to cohesive soils but I figured that was very very conservation, especially in the case of a difficult design in which friction becomes very helpful.
Thanks for the responses!
RE: Earth Pressure Coefficients for Stiff Clays