Kraft et al. (1981) details the results of axial loading tests on single piles and pile groups driven into a stiff over-consolidated clay at a site located on the University of Houston Campus. The piles were closed end tubular steel pipes with Young’s modulus of 210GPa, external diameter of about 274 mm, wall thickness of 9.3mm and penetration depth of about 13.1m (43 ft).
This case is analyzed with PileAXL program with adopting USACE method to estimate the ultimate shaft resistance and end bearing resistance of stiff over-consolidated clay. The soil parameters are based on the undrained shear strength profile presented by Kraft et al. (1981), which are interpreted primarily based on unconsolidated-undrained tests with simplified constant values for different soil layers.
PileAXL program calculates the pile settlement based on t-z curves for shaft resistance and q-w curve for end bearing resistance. For this case study, t-z curve as recommended by Coyle and Reese (1966) is adopted.
The following figure shows the ground profile, pile type, pile length and section size information. The calculated distributions of ultimate shaft resistance and end bearing resistance along the pile length are also shown on the same figure.
The calculated load settlement curve at the pile head is shown in the figure below. It also displays the information about the ultimate axial pile capacity, ultimate end bearing resistance and ultimate shaft resistance. This figure also shows the pile head settlement corresponding to the input specific axial load at the pile head.
The following figure shows the comparisons between the predicted settlement and the measured values reported by Kraft et al. (1981). It demonstrates the very close agreement between the computed and measured load-settlement values for the single pile.
