Applications of a Simplified Dynamic Load Testing Method for Cast-in-Place Piles

Dynamic loading tests take advantage of the high impact load that a relatively small mass can generate by falling from a preselected height. For driven piles, where the readily available driving hammer itself is the loading apparatus, this test method is particularly convenient. The uniform geometry and material properties of driven piles makes pile load and motion measurements and their interpretation relatively easy. For drilled shafts, however, the testing effort is somewhat more involved because a ram with a weight equal to 1 to 2% of the test load must be available and dropped from heights of 1 to 3 m by using a crane. Additionally, potentially irregular shape and non-uniform material properties of cast-in-place pile tops make accurate force measurements more challenging. This paper further describes how the dynamic testing procedure has been simplified and made more accurate by the APPLE (Advanced Pile Proof Loader/Evaluator) method, which combines the force measuring device with the loading system. In effect, the pile top force is calculated from the product of measured deceleration and mass of the drop weight; motion is also measured at the pile top. The paper describes two tests, conducted on different field sites, and presents correlations that further verily the soundness of this approach.