Dynamic pile testing has essentially replaced time-consuming and costly static load tests for the determination of driven pile capacities. Dynamic pile testing technology was introduced to the industry nearly 30 years ago. Since that time the technology and equipment used to perform the dynamic pile testing have gained acceptance from design structural engineers, owners, geotechnical consultants and most notably, pile driving contractors who have accepted dynamic testing as a cost-effective quality assurance tool. The American Society of Testing and Materials has developed a standard (ASTM:D4945) for the performance of Dynamic Tests. The Pile Driving Analyzer (PDA) is pictured in the photo, right.
As a test pile is being driven, the PDA displays and records dynamic measurements from strain transducers and accelerometers attached near the top of the pile, as shown in the second figure. For each hammer blow, the PDA processes signals from the gauges to calculate the hammer energy, pile stresses and pile bearing capacity. These results are displayed instantaneously on the PDA screen. The PDA can also detect pile damage during driving. A continuous driving log of the pile being tested (bottom illustration) and all of the dynamic data are stored on a disc in the PDA so later retrieval and analysis using the CAPWAP TM analytical software program can be performed as needed.
It is common knowledge today that the old method of using dynamic driving formulas for computing the amount of actual load a pile will support is highly unreliable. Dynamic driving formulas rely on visual estimates of pile penetration resistance and hammer stroke. The dynamic testing methodology AET offers utilizes actual strain and acceleration measurements from the pile. It has been rigorously compared to actual static load tests and proven to be highly reliable.
AET engineers have more than 20 years of field experience using the Pile Driving Analyzer. We have also served our deep foundation clients by assisting in the performance and evaluation of static load tests, preconstruction wave equation analysis, pile materials testing and production pile observation services. |
