5 NZ-6374CAT 5A major decrease in i

5 NZ-6374
CAT 5
A major decrease in impedance is apparent within a few metres of the pile top. The dynamic stiffness is
very low.
This decrease in impedance indicates a total discontinuity in the shaft at the indicated level. This type
of result is typical of piles that are cracked during excavation by mechanical digger. Such cracks are
usually very fine, indeed almost closed, and are generally horizontal across the shaft.
CAT 6
A decrease in impedance is visible at an intermediate depth. The stiffness value is normal to low and
the mean mobility is normal.
This indicates a weakness in the pile shaft at the indicated level. This could be in the form of a reduction
in section/waisting, a discontinuity or due to a layer of poorly compacted/contaminated concrete.
CAT 7
Very poor data quality such that the result cannot be meaningfully interpreted.
This can be due to cracking or poor-quality concrete within the top few centimetres of pile shaft or
inadequate preparation. The pile will need to be trimmed to sound concrete and re-tested.
4. ASSESSMENT OF BELL
Table A