text: Civil Engineering Photos » Dynamic Pile Testing
  Photo Credit: Nathan Shoemaker
  Shown here are the strain gauge transducer and accelerometer used for high-strain dynamic pile testing, there are two more gauges on the other side of the pile. The idea behind dynamic pile testing is that when the pile is struck with the hammer a wave propagates down the pile to the tip and back up. The wave is dissipated by dampening along the skin and toe. The strain data combined with the pile properties (modulus of elasticity and area) give axial force and the acceleration data can be integrated to find particle velocity, and since the wave speed of steel and concrete is reasonably known, the wave distance can be determined. Depending on the shape of the force and velocity graphs it can be determined if the pile is more of a friction or end-bearing pile and what the capacity of the pile is. The legitimacy of this testing can be proven by the reductions in factors of safety for deep foundations that AASHTO allows for when a high-strain dynamic pile testing program is implemented on a project.
  Tags: Deep Foundation
  Does dynamic pile testing offer any benefits when compared to full scale static load tests? Any disadvantages?
  It is a much faster test to run. Dynamic testing takes as long as it does to drive a pile so maybe 30-60 minutes/pile. A static load test can take 4-8 hours to set-up and complete. On the other hand Static Load test is still the industry standard and thusly a dynamic pile test program has to test usually twice as many piles. Don't quote me on this but I believe the Factor of Safety for driven piles with 1% of all piles being static load tested is 2.0. While for a high-strain dynamic test on 2% of all piles is 2.25. You'll get to learn a lot more about this I'm sure because G2 does high-strain dynamic testing.