K Preiss and A Caiserman. This paper was first published in GE’s May 1975 edition.
The possibility of the occurence of voids or lenses of soil in bored concrete piles and diaphragm walls is a cause of some concern to the civil engineering profession, particularly when the concrete is placed into a bentonite slurry. Several cases of failure as a result of lack of concrete in the foundation have been reported. The damage suffered to the building owner, to the contractor, and to the insurance companies can in such cases be considerable.
A number of methods of testing bored piles to locate possible faulty zones have been reported. These include core drilling, sonic testing, electrical resistance measurement, stress wave propagation and methods based on neutron or gamma radiation.