Design of Precast RC Piles by Pile Load Tests
Abstract
Piled foundations for a power development near Dhaka, Bangladesh have been designed from a series of Advance Pile Load Tests (APLT’s) which comprised on-site static and dynamic load testing of seven true scale test piles. The piled foundations of the Main Power Block were to be constructed on potentially liquefiable reclaimed land. The Main Power Block area was improved by sand compaction piling while the Substation structures were located in a ground partially improved by surcharging with sand stockpiles. The site soils are micaceous loose to medium dense, fine sand and silt. The site comprises 6 m of reclamation fill underlain by inter-layered alluvium. Following extensive site investigations and pilot studies of sand compaction piling, the APLT’s were conducted in both improved and partially improved ground. The key objective of the APLT’s was to quantitatively evaluate the effect of sand compaction piling on pile load capacity and to establish most economical design of piled foundations in both improved and partially improved ground. It was also necessary to take into account pile capacity reduction due to potential soil liquefaction in the partially improved ground. Overall the pile capacities interpreted from the dynamic and static load testing were consistent. Furthermore, interpretation of the static and dynamic load testing in conjunction with a SPT correlation method allowed optimisation of pile lengths and axial pile capacity. As a result, substantial savings were achieved in material cost and construction duration. This paper describes the site conditions, methodology of APLT’s and analytical design of the piled foundations. Moreover, comparison is made to a similar power development design to illustrate the benefits of pile design by APLT’s.