Utah Boring Contractor Ranks Pipe-Ramming Performance

Introduction

Auger boring and tunneling in the hard-packed earth and cobblestone river beds of Utah have never been easy. Even with years of experience contractors claim each job in these soil conditions brings its own special headaches and challenges. Anyone who has bored and tunneled in the western United States has sought better, faster and less costly ways of installing steel casing conduit under roadways and irrigation canals. Utah boring and tunneling contractor WILLCO Far West, a father and son partnership, believes that it has found a cost-efficient way — by installing pipe with HammerHead Mole units.

WILLCO Far West works primarily as a specialized subcontractor installing steel casing for a variety of utility service lines. The contractors currently have five crews throughout Utah and other Western states, employing the use of different sized auger-boring machines that can jack pipe from 8 inches to 60 inches in diameter. They started experimenting with their first pneumatic tool pipe-ramming projects in the summer of 1994.

Their adoption of this technology did not come quickly. Like most contractors, they took a sharp pencil to their productivity/cost calculations, seeking out the best labor - and maintenance-saving equipment. They knew that, when they bought new equipment, it had to work and it had to last. Because, if it were successful, that is where the profits would be.

Frank and Daren Willden of WILLCO Far West have tested pipe ramming extensively, documenting and comparing its productivity with that of the auger-boring and tunneling methods they have used for 25 years.

Background

One of the reasons the Willdens looked at pipe ramming was the increased specification of pipe ramming by engineering firms in their area. When designing utility installation jobs in Utah, these firms wanted to eliminate the possibility of voids created by auger boring under irrigation canals and roads.

According to Daren Willden of WILLCO, this apprehension may be misplaced. “The engineers worry about the cutting head getting out in front of the pipe in a jack-and-bore operation. But if crews know what they are doing and have the experience, this is not a big problem. Pipe ramming has entirely eliminated this concern.”

Soil Conditions

In Utah, a boring contractor can face anything from swampy conditions, to a clay and sand mix, to river-bottom cobble, to larger boulders and glacial till closer to the mountains. The Willdens have found that pipe ramming with the 8-inch and 12-inch HammerHead Moles work well in all these conditions, but especially well in the cobble.

Daren Willden commented on performance, “We’ve found that no machine will do everything, but the HammerHead Moles work especially well in cobble rock and extremely wet conditions with running water. A 16-inch casing installed by augering will accept a 4-inch diameter rock, but not much of it. It will plug up the auger flights. A 20-inch casing will accept a few rocks 8 inches in diameter, but not many of those either. We have, however, pipe rammed 20-inch steel casing in these conditions, and it has worked. The pipe either cracks the rocks, displaces them or swallows them inside the casing.”

Setup Time

WILLCO Far West has documented the setup times for the pipe-ramming jobs versus the auger-boring projects, and believes that pipe ramming is more cost-effective.

According to Daren Willden, “With pipe ramming, you don't need to have as big a pit as you do with auger-boring machines. The pneumatic tools are about 6 feet in length and an operator can add to this the pipe lengths to get the entry pit length needed. So the entry pit length is shorter than what is needed for auger boring. Since there is less equipment to haul, setup also takes less time.”

Crew Training

The skill, experience and judgment of the crew were reported to be crucial in a successful boring operation. But because there are fewer procedures with pipe ramming, crews make it up the learning curve much faster. Willden stated, “Though experience is still necessary for a successful job, crews experienced in boring can learn pipe ramming in far less time than it takes to learn auger boring. With pipe ramming, the crew only has to lower the pipe into the ground, attach the tool to the pipe, hook up the compressor, and level the tool and the pipe then away they go.”

Productivity And Accuracy

Recently, WILLCO rammed 410 feet of 20-inch casing under I-80 east of Salt Lake City, Utah, in very wet conditions in 4-to 6-inch cobblestone. On another project, WILLCO installed 110 feet each of 16- and 18-inch casing under the Blackfoot River. The 16-inch casing took nine hours. The 18-inch took 11 hours and was completed in a heavy rain storm. WILLCO has completed more than 40 crossings since purchasing the HammerHead Moles one year ago.

Willden explained that, when it comes to productivity rates, it all depends on the size of the pipe, the length of the job and the ground conditions. Willden said, “If the conditions toughen, any job will slow down. Unless you're the fellow that backfilled the road, you'll never know what's under it.”

Willden continued, “With pipe ramming, as long as you use a level when you ram your first sections of pipe, you can maintain desired accuracy, especially for shorter bores. At Ogden Defense Depot, we had to ram 60 feet with the 8-inch HammerHead and we came out only 1/4-inch off grade.”

WILLCO’s keys to success are the use of 1/2-inch wall or thicker casing and the use of bentonite to reduce friction. We can increase ramming distances by augering out the casing when progress slows. Above all, WILLCO has never had better technical support than we have received with the HammerHead Moles.”

Summary

In summing up his view of the market for pipe ramming, Willden added, “We feel confident we can push anywhere from 10-inch diameter to 18-inch diameter pipe up to 60 feet with the 8-inch HammerHead Mole and from 12-inch diameter to 30-inch diameter pipe with the 12-inch tool. For relatively short bores, because of the fast setup time, pipe ramming is perfect. You can be in and out in a day.

By: Richard A. Yach — Technical Writer Des Moines, Iowa