| Abstract: |
This paper presents an analysis of long, large-diameter bored piles’ behavior under static
and dynamic load tests for a megaproject located in El Alamein, on the northern shoreline of Egypt.
Site investigations depict an abundance of limestone fragments and weak argillaceous limestone
interlaid with gravelly, silty sands and silty, gravelly clay layers. These layers are classified as
intermediate geomaterials, IGMs, and soil layers. The project consists of high-rise buildings founded
on long bored piles of 1200 mm and 800 mm in diameter. Forty-four (44) static and dynamic
compression load tests were performed in this study. During the pile testing, it was recognized that
the pile load–settlement behavior is very conservative. Settlement did not exceed 1.6% of the pile
diameter at twice the design load. This indicates that the available design manual does not provide
reasonable parameters for IGM layers. The study was performed to investigate the efficiency of
different approaches for determining the design load of bored piles in IGMs. These approaches are
statistical, predictions from static pile load tests, numerical, and dynamic wave analysis via a case pile
wave analysis program, CAPWAP, a method that calculates friction stresses along the pile shaft. The
predicted ultimate capacities range from 5.5 to 10.0 times the pile design capacity. Settlement analysis
indicates that the large-diameter pile behaves as a friction pile. The dynamic pile load test results
were calibrated relative to the static pile load test. The dynamic load test could be used to validate
the pile capacity. Settlement from the dynamic load test has been shown to be about 25% higher than
that from the static load test. This can be attributed to the possible development of high pore water
pressure in cohesive IGMs. The case study analysis and the parametric study indicate that AASHTO
LRFD is conservative in estimating skin friction, tip, and load test resistance factors in IGMs. A new
load–settlement response equation for 600 mm to 2000 mm diameter piles and new recommendations
for resistance factors φqp, φqs, and φload were proposed to be 0.65, 0.70, and 0.80, respectively.
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