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RC Drilling in today’s Foundation Drilling Industry

A case study by Timothy W. Conn; President WVC Mincon
Lake Oswego Interceptor Sewer Reclamation Project, Oregon USA
Contractor: Advanced American Construction

The following case study relates to a piling job on Lake Oswego in Oregon in the Northwestern United States. WVC Mincon had the pleasure of developing some innovative drilling solutions, and supplying custom equipment to be used on this project in conjunction with Advanced American Construction.

Scope of Drilling: 
Install over 300 18” Piles with a 16” Rock Socket. The drilling was to be done from a barge through varying strata, from competent hard basalt, to clays, gravels, and suspended Boulders. A major component of the scope of this drilling project was the inclusion of all environmental controls for the complete containment of all spoils, debris and water used or produced during the Drilling Process.

Equipment Supplied:
WVC 72 R/C Rotator: 72,000 Torque with 6” Return and Discharge Swivel.
WVC Dual Air Supply Swivel for 14” Flange Pipe
WVC Dual Air Supply 14” Flange Pipe with 6” Return
WVC Dual Air Crossover Packer
Conventional 12” Hammers, 16” DTH Bits and 18” Under Reamers

The WVC72 R/C Rotator for this job was mounted via sled to American Piledriving Equipments 26” x 120’ Leads and Spotter. These were mounted onto an American 100 ton Crane with American Pile Driving Equipments hydraulic power pack. Using this configuration gave over 110’ of single pass Drilling. The drill string was made up of sections of WVC Dual Air Supply 14” Flange Pipe with 6” Return. The Bulk Head for discharge air supply was configured for use on the right or left due to the tightness of the job and the need to be able to position the water control barge on the port or starboard side.

The air supply manifold supplied to this job consisted of twin 2 ½” manual valves equipped with crossover pipe and valve, back flow valve and gauges for monitoring back pressure on the Jetting Sub, and Hammer Supply. The in line air Lubricator was connected to the Hammer Side of the supply manifold.

The water control barge for this job was equipped with two 950/350 compressors. The barge was also fitted with water tanks and spoils roll on boxes equipped with cyclones, and sand separation units.

The 12” Hammer equipped with an 18” under reamer was used to drill the 18” Pile Down to a 6 ft. minimum Socket Depth. While drilling, the pile was supported by a rabbit on leads at the top and a fixed swing table at the bottom. The penetration rate for this part of the operation was approximately 3 minutes per foot. The formation was solid basalt sloped at 5 to 10 degrees with varying mud’s and gravel.

The piles were lined up and set by the piling barge. The barge was equipped with a state of the art GPS positioning system and the American Piledriving Equipment Variable Moment Vibro and Hydraulic Power Pack. This system provided one of the fastest locate, pitch, and vibro set ups for installing piles for jetty, bulk handling dock marine pile projects. The combination of the best equipment from GPS to Vibro, in the hands of competent pile Bucks was evident.

The drilling barge at this point is then moved to the pile location for muck out and drilling of the rock socket of the pile. The muck out procedure is done with a Hammer and a 16” bit positioned off the mud line by 5 feet. Water is pumped through the Hammer at 50/75 gpm using slow rotation. The Air supply is turned on to the Jet Sub and air is slowly added to the hammer. The drill string is then lowered to the toe depth. The penetration rates through muds, clays and gravels were approximately 2 minute per 20 ft. Upon reaching the toe depth the water volume is cut to 25 gpm. The hammer and bit are advanced through the toe to Drill the Rock Socket. The Penetration rate was 2/3 minutes per foot in Competent Rock.

The deep water piles of 150ft plus were a little more difficult to drill. Due to skin friction in the clay bands, and gravel areas as some piles were mucked out they needed another vibro operation and splice to get the required toe depth. These were all still accomplished.

In all cases on this job the equipment supplied by WVC Mincon met or exceeded the expectations of Advanced American Construction.

This is just a short over view of the drilling procedures, and tooling used on the project. The project is ongoing with 60% of the drilling complete at the time of this article, and is maintaining schedule.

The successful drilling operation on this project is not just related to the tooling and drill procedures supplied, but also to the commitment from Advanced American Construction Management and Field Personnel in the sourcing, implementation, training and use of the correct equipment.

For WVC Mincon it was a pleasure working with and training professional competent personnel. The drill barge crew’s grasp of the drill concept and eventual ownership has been a key in the ongoing success of this job. WVC Mincon would like to say a special thanks to the following people for contributing to the success of this project:

Advanced American Construction
Dee Burch - President, Mike Johns - VP Operations, Jim Mole - Drill Barge and the Drill Barge Crew

American Piledriving Equipment
Dave Yingling – General Manager and Kelly Goranson
Focused on providing the complete Reverse Circulation drilling solutions package to today’s foundation drilling contractor the WVC Mincon range of products covers the following:
-          Hydraulic Rotators
-          Drill Pipe
-          Stabilizers: Fixed or bearing configuration
-          Jet Subs
-          Air Swivels
-          RC Hammers and Bits from 12”(305mm) to 42”(1067mm)
-          RC Ring Bits
-          Multi Drills from 49” (1250mm) to 118” (30000mm)
-          Concentric Under Reamers

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