Cross-hole sonic logging

The CHUM (Cross-Hole Ultrasonic Monitor) enables advanced integrity testing of deep foundations and other concrete structures, bored piles, diaphragm walls, barrettes, cast-insitu piles and columns.

Cross-Hole integrity testing is performed in access tubes cast inside the pile, so the equipment is brought close to potential defects. The method utilises ultrasonic frequencies, with typical wavelengths of 50 to 100mm. This enables the discovery of minor defects and also allows the wave to travel in any direction.

Pulses generated by the ultrasonic pulse generator are converted into ultrasonic waves by the transmitter probe and are received by the receiver probe. After conditioning, signals are digitised and stored.

The meter-wheel, acting as a depth sensor, provides the vertical (Y) axis for the display and First Arrival Time (FAT) and relative energy are displayed. Variations in arrival time and signal strength highlight areas requiring further investigation.

To investigate problematic areas within pile shafts PMC are now able to offer tomography imaging which may eleviate the need for expensive, time consuming coring of the shaft.