Coefficient of Friction b/t clay and concrete base
Coefficient of Friction b/t clay and concrete base
(OP)
Anyone have a table or a reference? I have a sand reference but nothing on clay? Also, is this dependent on the adhesion like a pile?
Thanks.
Thanks.





RE: Coefficient of Friction b/t clay and concrete base
As for adhesion, I have always used 0.6 times the cohesion for cast in place concrete.
Of course any resistance value should be limited by the less of the adhesion and friction values.
RE: Coefficient of Friction b/t clay and concrete base
NAVFAC DM 7.2 Table 1 p63 shows friction angle of 17-19 degrees for concrete/cohesive soils. It's common practice to take the coefficient as 0.3.
Jeff
Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com
The views or opinions expressed by me are my own and do not necessarily reflect the views or opinions of my employer.
RE: Coefficient of Friction b/t clay and concrete base
RE: Coefficient of Friction b/t clay and concrete base
RE: Coefficient of Friction b/t clay and concrete base
That said, for most retaining wall situations, I would use the friction value between the wall and the soil. If I had actual lab testing consisting of drained test results for the soil at the bottom of the wall, then I would use 2/3 of the drained friction angle plus 0.3 or so times the cohesion.
If I had a short term loading condition, then I would just use the adhesion.
My experience with clay soils and retaining structures, indicates that most wall designs are not controlled by base sliding, but are controlled by global stability or overturning. Where it gets ify is when you have a clayey silt kind of soil with a relatively high drained strength. In those cases sliding of the retaining wall can controll and you have to make a judgement on how much, if any, of the adhesion to include.
I would also point out that it is relatively simple to add a shear key to the bottom of footing in clay or silty clays. This pretty much gets rid of the question of how much of the adhesion to use since a good portion of the potential failure plan passes throught the soil and not at the boundry between the materials.