One way would be to apply the Pais & Kausel, 1988 static vertical impedence formula used for shallow foundations with an embedment. In this case the embedment effect would prevail. The resulting spring stiffness may make sense if we see the slurry wall as a single, huge spring.
Do you need spring stiffness (dimensions: force/lenght) or the coefficient of subgrade reaction (dimensions: force/lenght^3)?
What are width, lenght and depth of the slurry wall(s)? Elastic and Shear moduli of soil? Any results of load tests?
I'm interested since I never came across such a problem. I would do just as above first and judge if the result is reasonable.
Thanks McCoy for your response. Not sure if this model would be appropriate though - talking about a 3' wide x 120' deep wall here. Wall actually made up of tangent circular bearing elements similar to ACIP piles. The question essentially is the spring that would replace the pile springs if indeed the foundation were made up of discrete pile elements spaced say 3D apart.
gfeel, is that a continuos wall or just detached elements?
I'll ruminate about it, if there is no simple solution I'm afraid you'll have to do it rigorousluy by the definition: K = W/s where W is the load in units of force, s the settlement in units of lenght. In lieu of load tests the settlements must be calculated by the elastic theory or FEM methods.