Sonic drilling provided new technological approach to installing Mebra drains

In 1983, the British Columbia Department of Highways had begun approach ramp construction for a major bridge across an arm of the Fraser River, near New Westminster, BC.

Geotechnical engineers involved in the planning and design decided that installation of vertical wick drains would speed up fill consolidation and thus economize on final construction costs. In cooperation with Nilos Canada Ltd., the Mebra drain supplier, MARL Technologies developed a new installation method. 

Mebra drain is a three inch wide corrugate material, sleeved with  fibre envelope of known permeability.  The material was supplied in rolls of 200 metres. (656 feet).

MARL designed and fabricated a 65 foot mast / drill rod which was threaded with the wick. The drill rod was inserted to the required depth by a sonic drill head attached to the boom of a large hydraulic back hoe. Installation of a 40 foot drain was accomplished in a matter of seconds.  

The sonic drill head vibrated the drill rod with a 150 hertz vibration that lessened the effective stresses in the soil near the tip and allowed for rapid insertion. The drill rod was withdrawn, leaving the Mebra drain in place and uncontaminated by a drilling fluid.