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 in situ 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.

A 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 ESG offer tomography imaging, alleviating the need for expensive, time consuming coring of the shaft.

Tomography supplements the traditional sonic logging profiles by combining arrival time data from all profiles and performs a curved ray analysis of the data.

The output is displayed in 2D or 3D model viewers to help identify defects.