Capacity Assessment of Steel Tubular Driven Piles-Paper

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The paper investigates time-dependent capacity gains in a 1,066 mm diameter steel tubular pile driven through predominantly silty sand on India’s Bay of Bengal coast. Driving disturbs the surrounding soil and generates excess pore pressure; as this pressure dissipates, effective stress and pile resistance can increase. This increase, known as pile setup, is often driven mainly by shaft friction.<br /><br />The test pile was driven 23 m and assessed using high-strain dynamic load tests (HSDLT) at end of initial driving (EOID) and during restrikes at 2, 7 and 119 days. Dynamic measurements were analyzed using CAPWAP. A static compression load test was also conducted after installation. The pile did not reach failure under the maximum applied static load of 9,045 kN, and its maximum settlement was 20.87 mm.<br /><br />Dynamic testing showed substantial capacity growth after driving: reported ultimate capacity increased from 4,158 kN at EOID to 7,104 kN at the 7-day restrike. The static test’s interpreted ultimate capacities ranged from approximately 15,900 to 35,298 kN, depending on the interpretation method. The authors report that capacity gains were predominantly due to increased skin friction, while end-bearing resistance changed little. They estimate a site-specific setup factor of about 2.16, consistent with reported values for silty sand.<br /><br />The study concludes that pile capacity can increase markedly with time after driving, and that setup should be considered in design where schedules and testing permit. The proposed factor is specific to the site and should not be applied universally.

Keywords

pile setup

time-dependent capacity

steel tubular pile

silty sand

high-strain dynamic load test

CAPWAP

shaft friction

end-bearing resistance

static compression load test

Bay of Bengal coast