These methods are used mainly for geotechnical, environmental, or archaeological sampling, and are ideal in tailing dumps, sand clay, silt, and peat.
Vibrating coring methods and how they work
- Sonic drilling is a soil penetration technique that applies the principles of Bingham’s Law to the luidising of porous materials. Using a sonic head, drill casings and rods are brought to a vibration frequency of 100–200 Hz.
Waves are transmited through the drill string to the end of the casing and relected, causing the casing to stretch and thin, and to shorten and thicken. This occurs 100–200 times per second, and the intense vibration causes a very thin layer of soil directly around the drill rods to luidise. The luidised soil zone extends a maximum of 5 millimetres from the rod. The soil in the inluenced area behaves like a luid, dramatically reducing the friction between the drill rod and the surrounding soil and allowing very rapid penetration. The same friction reduction applies to the inner surface of the soil sampling tool, enabling the collection of very long sample cores.
In addition to the vertical vibration, sonic drill heads can also rotate to easily make up and break drill rods, and to cut concrete or asphalt.
- Vibrocore drilling is similar to sonic drilling and is used to retrieve core samples from beds of bodies of water such as seas, rivers, lakes, dams, or oceans.
- The drilling unit incorporates an electric or hydraulic vibrating head mounted in a frame that is lowered to the bed of the water body. It is operated remotely to recover 2 to 3 metres of core and then retrieved to the boat or barge. The system relies on the weight of the vibrating head to enable the core barrel to penetrate the waterbed