Axial Load Behavior of a Driven Cast-In-Situ Pile in Sand

Driven cast-in-situ (DCIS) piles are a popular choice amongst piling contractors due to the ability to readily adjust pile lengths to suit the depth of penetration required. Despite their widespread use, there is a dearth of published data on the axial load behavior of temporary-cased DCIS piles, particularly in cohesionless soils. This paper reports the results of a static compression load test on a 340 mm nominal diameter, 5.75 m long DCIS pile in a dense sand deposit in Shotton, Wales. The test pile was instrumented with vibrating-wire strain gauges at various levels to determine the shaft and base resistance during loading. Analysis of the test results showed that pile behavior was predominantly end-bearing, with the base resistance accounting for approximately 81 % of the total capacity at a displacement of 10 % of the pile diameter. The pile exhibited a stiff stress-displacement response during the initial stages of loading due to the level of pre-stress applied to the soil beneath the base during driving of the steel installation tube. The displacement required to mobilize the shaft resistance was similar to that reported for preformed displacement piles, with a peak local shaft friction of 105 kPa occurring near the base of the pile which diminished with increasing distance from the tip. Finally, the load test results were compared with two popular CPT-based design methods (LCPC and Imperial College methods) for displacement piles in sand. Despite having specific empirical correlations for DCIS piles, the LCPC method significantly under-predicted the capacity of the test pile