Strong Rock [Turner, 2006]

The p-y relationship is bilinear, defined by Eqn. (1) and Eqn. (2) , extending until it reaches the ultimate resistance in Eqn. (3). If $p_u$ is attained, a brittle fracture is assumed.

$$\tag{1} p = 2000S_uy \quad for \quad y \leq 0.0004b$$

$$\tag{2} p = 100S_uy \quad for \quad 0.0004b < y < 0.0024b$$

$$\tag{3} p = p_u = bS_u \quad for \quad y \geq 0.0024b$$

where,

$p$ = horizontal resistance per unit length $y$ = horizontal displacement $b$ = diameter of the shaft $S_u$ = one half of the $q_u$, unconfined compressive strength $p_u$ = ultimate resistance per unit length

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[Turner, 2006] Turner, J. P. (2006). Rock-socketed shafts for highway structure foundations, volume 360. Transportation Research Board.