In CAPWAP®, what factors should be used for radiation damping for shaft and toe?

First, you should read the correlation paper below, that discusses radiation damping. There are also some other papers on radiation damping on our website’s Reference library

•Likins, G. E., Rausche, F., Thendean, G., Svinkin, M., September 1996. CAPWAP Correlation Studies. Proceedings of the Fifth International Conference on the Application of Stress-wave Theory to Piles 1996: Orlando, FL; 447-464.

For the shaft, a correlation study was performed and discussed in the 1996 paper. The recommended values for shaft radiation damping are given by CAPWAP®. The recommended values are proportional to the three largest shaft resistances, so there are no “fixed values” to recommend. Use the CAPWAP® recommended limits (particularly do not go below the lower recommended limit).

We are using radiation damping (particularly for shaft) for open profile sections (open ended pipes and H piles in soils – H not driven to rock) to try and compensate for the interior plug slipping.

Since it has not been studied, there is no advice for values to use for toe radiation damping. Unless you have supporting experience in similar soils, toe radiation damping is not recommended.