Vibracoring (or vibracoring) is a technique for collecting core samples of underwater sediments and wetland soils.
he vibrating mechanism of the vibracore, sometimes called the "vibrahead", operates on electrical power and can be run from a small portable generator.
The attached core tube is driven into sediment by the force of gravity, enhanced by vibration energy. When the insertion is completed, the vibracore is turned off, and the tube is withdrawn with the aid of hoist equipment.
The frequency of vibrations can be adjusted in the range of 3,000 to 11,000 vibrations per minute (VPM), and the amplitude of movement is on the order of a fraction to few millimeters (mm).
These vibrations cause a thin layer of material to mobilize along the inner and outer tube wall, reducing friction and easing penetration into the substrate.
The liquid spaces in the matrix allow sediment grains to be displaced by the vibrating tube. Vibracoring works best on unconsolidated, waterlogged, heterogeneous sediments and soils. Silty sediments of mixed grain size are easiest to core.
Vibracoring is less effective for relatively dry clays, packed sand or any consolidated (cemented) materials.
The custom built vibracore designed and built by Diving Services New Zealand Ltd is very portable, and can be used from a relativity small vessel /platform. The unit can be adapted to take almost any size core/tube type.
The Unit has a sealed 70 meter cable and can be setup for use with of without a diver.