Denver contractor and Link-Belt cranes drill through the Rocky Mountains
Lexington,
Ky.
(March, 2000) — Denver-based Coggins & Sons combines their experience with the
latest in high-capacity, duty-cycle cranes technology to drill caissons in
the daunting and beautiful Rocky Mountains. The caisson project they are
on is the Veterans’ Hospital new parking garage project in downtown
Denver.
Coggins drilled 100 shafts for the installation of the deep-foundation piers. The multitude of piers is necessary because of the load that will be incurred on the ground from the new multi-level parking garage. To tackle the job of drilling 12 caisson and three tiebacks the contractor added two, Link-Belt LS-208H II 80-ton capacity lattice boom crawler cranes to its fleet. The Link-Belt crawler cranes are necessary for carrying out various types of geotechnical projects, including the new parking garage, the company has under contract.
Since the 1990’s there has been responsibility
placed on drilling contractors to supply design-engineering expertise for
improved geotechnical methods that enable the project to be completed more
cost-efficiently. “We were willing to meet the need for engineering
services because it has enabled us to expand our business,” says Larry
Coggins, president, Coggins Construction. “This has been especially true
with clients in the private sector.”
The various geotechnical engineering and contracting projects Coggins performs are deep-foundation projects, earth retention systems, and tieback anchoring in sub-surface walls, micro-pile installation and large diameter deep well drilling.
The company is most active in deep-foundation projects. With deep-foundation systems projects being head of the contractor’s activities and coupled with continuous business growth in this activity, the addition of two new duty-cycle cranes was a necessity. Most of the deep foundation contracts call for large-diameter, deep-well drilling to an acceptable stratum (level) in the earth.
Caisson foundation (or non-displacement pile) drilling is accomplished by using a strong and reliable duty cycle crane with a drilling attachment. To reach competent ground (i.e. ground capable to support the load it is intended), the shafts are being drilled an average of 50 feet deep. The shafts’ diameters vary from one to six feet. These variances are determined on the changing soil competency found where the individual pier bearing point is to be located. The soil conditions are classified as clay, sandstone or sandstone-bedrock. Outfitted with a Stewart-Stevenson drill auger on an 80-ton capacity Link-Belt LS-208H II crane equipped with angle boom, the shafts were drilled with little problem. Upon completion of the drilled shaft and using the same crane, a site fabricated, steel reinforcing bar cage is lowered into the shaft. Concrete is poured into the shaft until it is completely filled and the steel cage is embedded.
The productivity in an eight-hour shift ranged from three to five shafts. For tougher soil conditions with rock, a carbide-tipped auger was used in the drilling. The crane and auger system bored the holes very efficiently. That includes incompetent rock with an unconfined compression strength value of up to 12,000 pounds per square inch. (p.s.i.)
Coggins’ projects stretch through the Rockies and Midwest, including Arizona, Colorado, Kansas, New Mexico, Utah and Wyoming. One of the more challenging projects Coggins recently completed was the Aspen Highway 82 project where 190 caissons were drilled in solid rock. The caissons ranged in size from 24 to 36 inches in diameter. Additionally, 30,000-sq ft. of earth retention was accomplished by installing tiebacks and shotcreting the surface for permanent stabilization.
Coggins also performed work at the new Denver International Airport where they drilled 6,000 caissons, Coors Field and the new Pepsi Center. After 41 years of active geotechnical engineering and contracting, the Denver-based contractor is still growing. Today the company is one of biggest of its kind in the Rocky Mountain region.