Rock In Colorado Challenges HDD Contractors

September 2012, Vol. 67 No. 9

"Rotating the reamer into the hole was still rough but it was different this time,” Jim explained. “You could hear the rock being destroyed as the tool moved ahead. Loose cobble and pieces of boulder were chewed up as the RockReamer closed in, trapping fragments between itself and the formation ahead, clearing a 24-inch path all the way down and into the solid rock. We had the best hole possible through the trouble zone and needed to complete the 24-inch pass without tripping. I knew the RockReamer cutters could hold up with the protection of our turtle shell."

Continuing, Jim noted that reaming was steady through the rock at a pace of four or 5 joints a shift. Circulation was never regained and the source of available water changed a couple times, slowing the process. The progress continued, placing just under 280 reaming hours on the 24-inch cutter set. The ream, back up through the entry side cobble and boulders, continued without incident, with the fabricated shield working just as it had through the exit side. The pilot hole and reaming phase were now complete but the hour of reckoning was at hand. Nothing mattered without a successful pullback of the product line.

Another R8 RockReamer was fitted with two-inch TCI cutters and a Brotherton-made shield was placed ahead of the swivel, pull-head and 16-inch product line.

Jim pointed out that the only way this would work is if the boulders and cobble had been ground-up and cleared. If any of it had slipped past the RockReamer or dropped into the hole, it could render the final task impossible.

He said, “About 7:30 a.m. the pull-head was ready and the rig applied tension, waking the drill string and pulling the 16-inch product line into the hole. One joint in and hearts stopped. A large boulder slipped! You could hear it hit steal and the torque spiked.”

Jim placed his hand on the drill string asking for slow rotation, before making the call to continue. "You could feel it in the rotation,” he said, “As pull was applied, you could hear it grinding away as the cutters chewed and crushed the rock. We decided to keep going. The chatter lessened, then ceased, as the line continued forward through the boulders and into the solid rock.”

Just one weld and 12-hours later, the growing crowd of cheerful business owners stood with the crew as they witnessed the 16-inch product line extend into the entry pit.