283757893275

128 Barry’s Advanced Construction of Buildings
(b)
(a)
Photograph 3.10 (a) Dynamic load testing method and (b) sonic integrity testing (http://
www.roger-bullivant.co.uk).
Sonic integrity testing
Sonic integrity testing is normally used on CFA, CHD or other piles foundations formed
using in situ concrete. The integrity method is fast and reliable. A large number of piles
can be tested in a single visit. The pile determines the reliability, morphology (form and
composition) and quality of construction of the pile.
Before the pile can be tested, it must be sufficiently cured, free of latence and trimmed
back to sound concrete. It is preferable to carry out the test at the final cut-off level of the
pile. A small hand-held hammer is used to strike the pile. A series of low strain acoustic
shock waves are sent through the piles. As the waves pass down the pile, the sound waves
rebound where changes in impedance occur. The rebound (echo) is then recorded by a
small accelerometer (instrument for measuring speed and acceleration), which is held
against the pile head. The response is monitored and stored, and a graphical representation
produced for immediate inspection (Photograph 3.10b).
Static load testing
Static load testing is used to determine the displacement characteristics of a pile. All piles
are suited to static load testing. Static load testing frames are assembled specifically for the
test. Major piling contractors assemble frames capable of accommodating loads up to
4000 kN (Photograph 3.11).
A known load has to be applied in the form of kentledge (loaded test frame) or tension
pile reaction. Load can also be applied by fixing a frame to piles already installed in the
ground. Other piles can then be tested against the frame load. Once an adequate reaction