What is sonic drilling?

Sonic Drilling uses high frequency vibrations (0 – 150 Hertz) generated in the drillhead by two out of balance rollers that cause the drill pipe to vibrate. The rollers are synchronised to ensure that the vibrations are transmitted vertically down the drill string to the bit. Aided by these vibrations, even a small machine can exert many times it’s own weight to the cutting edge of the bit. Sonicbore’s 2.5ton drill rigs exert 14 ton of downward pressure on the bit.

When the drillhead is in sonic mode, the soil particles that come into contact with the drilling tools are fluidised reducing friction and allowing rapid penetration without the need for a flushing medium. This fluidisation only occurs within a few millimetres of the drilling tools and therefore does not distort the samples in any way. Even in very soft estuarine deposits layered sections of sand and silt no matter how fine can be recovered undisturbed and logged by the site engineer.

Core recovery is normally near 100% and as there is no flushing medium the core is not contaminated by drilling activities. This drilling method can, in the right ground conditions, attain depths of up to 30mtr. and carries on down long after standard sampling methods have met refusal.

In the USA some companies have successfully used sonic drilling techniques to great depth and through very hard bedrock however the sonic drilling operations carried out by sonicbore is for sampling superficial deposits such as clays, silts, sand, gravel, and soft/weathered rock. In general there needs to be pore space in the material to be sampled. When in the sonic mode, the sonicbore drillhead does not rotate.