CAPWAP ™ Analysis
An essential tool with PDA, Geo Dynamics has been a pioneer in introducing Case Pile Wave Analysis Program (CAPWAP) for pile foundation testing in the country. We demonstrated for the first time in India in 1998 that it is possible to obtain skin friction and end bearing from High Strain Dynamic pile testing as also pile profile.
CAPWAP is mandatory to verify PDA field results for all bored and cast-in-place driven concrete piles, CFA piles at any jobsite. CAPWAP should also be used for at least the first few driven piles at any site monitored for end of driving and should also be used for all re-strike tests at any project site to correctly estimate the pile capacity.
The CAPWAP program is an analytical method that combines measured field data with pile wave equation type procedures, to predict the pile’s static bearing capacity and soil resistance distribution. Measured force and velocity data is directly input from the PDA. Based on the measured velocity data, the program computes force required to induce the imposed velocity. Both measured and computed forces are plotted as a function of time and the iterative analysis is continued till there is good agreement between both the curves. If the agreement is not satisfactory, the soil resistances at the pile point and along the pile are adjusted until a good match is obtained. This gives correct estimates of the actual static pile capacity measured during field testing, and also the friction and end bearing components. A good match implies a Match Quality number less than 5 for bored piles and almost always less than 3 for driven piles.
CAPWAP requires expertise and understanding of pile / soil / hammer behaviour. It is the key to understanding and evaluating data obtained from PDA tests. Information like end bearing, skin friction, pile integrity, total pile top displacement aids the designer to take effective and quick decisions.
Geo Dynamics has successfully demonstrated its expertise by correlating CAPWAP results with static load tests for a diverse range of projects in the country and abroad. Our clients have written technical papers based on our reports and analysis. Please refer to the LIBRARY of technical papers for details.
It is important the testing companies are able to analyze and explain CAPWAP results, compare them with soil, design and provide solutions to owners, consulting, contracting companies so as to have a good match between design, workmanship and quality control at project sites.