Stiff Clay without Free Water (Welch and Reese) [Welch and Reese, 1972]

Following p-y curve is recommended by [Welch and Reese, 1972] for stiff clay under static loading.

(1)

where, p = horizontal resistance per unit length pu = horizontal ultimate resistance per unit length y = horizontal displacement y50 = deflection at one-half the ultimate soil resistance

y50 is defined as:

(2)

ε50 = the strain corresponding to one-half the maximum principal stress difference b = pile diameter

Ultimate horizontal resistance pu defined smaller of the values given below.

(3)

(4)

where γ = unit weight cu = undrained shear strength ca = average undrained shear strength over the depth z z = depth J = factor, taken as 0.5 by default

Beyond point where displacement, y, equals to 16y50, p is equal to pu for all values of y.

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[Welch and Reese, 1972] Welch, R. and Reese, L. C. (1972). Laterally loaded behavior of drilled shafts. Technical Report 35-65-89, Center for Highway Research. University of Texas, Austin.