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 The drill rod was withdrawn, leaving the Mebra drain in place and uncontaminated by a drilling fluid. 

Canada's first tension leg motion compensated geotechnical drill

In response to a need from a major oil firm, MARL Technologies designed and fabricated the first tension leg motion compensated geotechnical drill in Canada. 

Designated the DGD 2000 (deep geotechnical drill 2000 feet) the machine was very successful in Canada's Beaufort Sea. 

The petroleum explorers in the Beaufort had developed a sophisticated system of artificial islands and refloatable caissons from which to drill their exploratory and development wells/ Geotechnical investigation was required to determine subsea borrow areas of dredgible material and foundation conditions, at the specific exploratory drill sites. 

All activity had to be conducted during a very short open water season, usually defined as 90 days in length.  The DGD 2000 was designed for quick and efficient operation. The drill was mounted on a 45 foot highway trailer which facilitated ease of movement to and from the ocean for essential seasonal maintenance and repair. 

The drill was equipped with CDP wireline core drill pipe which adapted very well to wire line operation of geotechnical tools. 

The flat dilatometer was used extensively to garner geotechnical parameters for island foundation design. The dilatometer readings were fed into an on-board ship computer, providing instant plotting of geotechnical parameters. 

Cathedral Mountain

The main line of Canadian Pacific Rail, just west of Field, BC, is subjected to periodic wash outs. The wash outs are caused by sub-glacial build up of melt water and subsequent debouching downslope to the tracks. 

Cathedral Mountain is a 10,000 foot peak topped by several small carapice type glaciers. Engineers suspected the sub-glacial periodic draining of meltwater from the 9, 500 foot level on the mountain was the cause of CP Rail's problem.

A MARL Technologies-designed heliportable drill was dispatched to the mountain glacier. The object of the drilling was to determine the ice thickness, the dpeth of water under the ice and the nature of the bus glacial soil conditions. 

The problems of mobilizing equipment and then having it operate at the 9000 foot elevation combined with the potential for exceedingly hazardous weather conditions provided a logistical challenge, but the MARL drill performed well. The project was completed within the allotted eight days and on budget.