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Lateral Stiffness of Soil

Lateral Stiffness of Soil

Lateral Stiffness of Soil

(OP)
Hi all!
I am working on foundation design for bridges, and have question. My question is how to find a good stiffness constant of laterallly loaded drilled shaft for finite element method. I looked at the books, there were at least 10 different method. I do not know which one is the most efficient. Would any one tell me how to find the best soil stiffness of laterally loaded pile?

Another question is how to model the pier to find out the max. moment and displacement on top of soil. I have big scour. it makes a long slender column with different cross sectional area of drilled shaft. Would anyone tell me how to model this case? I used the point of fixity for short drilled shaft of pier. for Tall column with different cross sectional area of shaft case, can i do the same approach?
(column length is longer then drilled shaft length)
 
Thank you very much

young-chul

RE: Lateral Stiffness of Soil

According to a paper by E.Czerniak , "Design Criteria for embedment of Piers" (old paper 1958), the recommended lateral soil pressure (in unit of pounds per square foot, per food depth) are :

Loose organic/mud = 0
Soft clay = 100
Compact inorganic siand and silt, sandy clay, silt = 200
Compact fine sand = 250
medium stiff clay, compact coarse sand/fine sand = 300
hard dense clay, compact well graded garvel = 400
medium hard caliche = 500

Ultimate lateral resistance of soil for purely cohesive soil increases from surface to about three pile diameter, and then constant at 8 to 12 times Cu times D.  For c-phi soil, ultimate resistance is given by Brinch Hansen
where pu = qK1 +cK2
q= vertical O/B pressure
c = cohesion
k1 and K2 are factors, a function of phi and z/d of soil.

We usually are using Brom's equation for design of short and long piles to determine laterally loaded piles. It is divided into 2 soil types : cohesive (clay) and cohesionless (sand) soils.

regards

RE: Lateral Stiffness of Soil

(OP)
what about if i want to find out the spring constant for modeling purpous. how can i get the spring constant. please tell me some examples. (i am entry level bridge engineer. please understand me.)

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