Dynamic pile testing and analysis are routine procedures in modern deep foundation practices. Dynamic Pile Monitoring is based on the Case Method of pile testing and is known as High Strain Method. It is covered by ASTM D4945 Standard Test Method for High-Strain Dynamic Testing of Piles.

Dynamic testing measures strain and acceleration near pile head under a hammer impact provides the basis for a complete analysis of the driving system-pile-soil condition. When the pile driving hammer impacts the pile top, accelerometers and strain transducers attached to it obtain data that is converted to velocity and force readings. Force and acceleration measurements taken near the top of a pile provide necessary information to determine:

• Mobilized pile capacity followed by further data analysis using CAPWAP
• Hammer performance
• Maximum driving stresses
• Pile integrity

During WEAP analysis various assumptions are made regarding hammer performance and soil parameters (available geotechnical information). These assumptions are verified using PDA and CAPWAP results; hence re-calibration of WEAP analysis is performed.

"... Before the project started, I was unconvinced that the use of PDA would be a cost-effective benefit to the project. It turned out to be well worth the cost as it frequently provided key evaluations at times when very costly situations required immediate decisions." Walter Grantz Chief Engineer of the Chesapeake Bay Bridge and Tunnel Project.

The Pulse Echo Test, also known as Pile Integrity Test, Sonic Echo Test and Low Strain Test, is normally performed after pile installation and curing. Pulse Echo Integrity Testing is a non destructive pile testing method that evaluates the integrity of auger cast-in-place (CFA) piles, drilled shafts, driven concrete piles, concrete filled pipes and timber piles. It detects potentially dangerous defects such as major cracks, necking, soil inclusions or voids and, in some situations, can determine unknown lengths of piles that support existing bridges or towers.

If major defects exist, the test estimates their magnitude and location; it may also estimate pile length. The impact of the hand held hammer at the pile head generates a compressive stress wave in the pile, and an accelerometer placed on top of the pile monitors the motion associated with this wave. The stress wave propagates down the pile shaft, and is reflected when it encounters either the pile toe or a non-uniformity of the shaft. These reflections cause a change in the acceleration signal measured on the pile top, which is picked up and processed by the Pile Integrity Tester (PIT) equipment and interpreted.

It provides following benefits:

• Minimal Pile Preparation
• Simplicity
• Speed of Execution
• Low Cost
• Can be performed on 100% of the piles on a given job site