Two-tier Bidirectional Static Load Testing for Pile Capacity Evaluation

In recent decades, there has been a significant increase in the construction of high-rise buildings due to the use of highcapacity foundation piles.Multistage (bi-level/two-tier) instrumented bidirectional static load tests (BDSLT) must be used to verify the capacity of these piles.This article describes the successful execution of an instrumented bi-level bored pile test socketed in the layered rocks of a high-rise building on Palm Jumeirah Island, Dubai.In order to ascertain the behaviour of the pile-rock interaction, a 1200mm pile at a depth of 25.60m was instrumented using ten levels of vibrating wire strain gauge technology and load tested up to 67596 kN using 6x9000kN sacrificial hydraulic jacks in two levels.The settlement recorded was 39.50mm, and the unit shaft friction calculated was in the range of 1000 kPa at the ultimate test load.It was found that the side resistances of the rock layers were higher than the values initially selected for the foundation design, indicating that the results of this bi-level load test accurately represented the true state of the subsurface.The design skin friction values were modified, considering the pile test and ground results, to provide the project with an economically feasible outcome.