A 9-in.-diameter steel pipe pile is driven into medium-dense sand to a depth of 30 ft, then load tested (for this site, the soil unit weight is 110 pcf, the angle of internal friction is 37° and...

A 9-in.-diameter steel pipe pile is driven into medium-dense sand to a depth of 30 ft, then load tested (for this site, the soil unit weight is 110 pcf, the angle of internal friction is 37° and groundwater is below the embedded pile). The failure load is 70-kips (test loading when large settlement commences). Based on the small pile tip end area, assume the pile end bearing is negligible and the pile functions as a friction pile.

(a) Perform a back analysis (effective stress condition) to determine the value of the beta-coefficient (β) for the pile type and soil conditions. For this analysis, assume the ratio of δ/ is 0.70.

(b) Estimate a value for K_f
(the final lateral pressure coefficient for the soil zone surrounding the pile shaft).

(c) Estimate a value for K0 (the preconstruction lateral pressure coefficient), assuming the pile installation procedure significantly densifies the sand so the ratio of K_f
to K₀
is 2.