Auger Boring In Tandem With Pipe Rammers
No one tool is perfect for every application. In the world of trenchless installation, many contractors who are accustomed to performing larger bores with augers have discovered the advantages of using pipe rammers in assisting or completing problem or difficult bores.
Although pipe rammers have been widely used in Europe for decades, awareness and use of the trenchless tool has only recently gained wider acceptance in North America. Contractors working in the most difficult soil conditions were the first to be attracted to the idea of incorporating as pipe rammer with their fleet of augers. By focusing on the bottom line of efficiently completing bores, these innovative contractors have positively positioned themselves in their perspective markets.
One contractor in particular, Frank Helm of Helm & Sons, Salt Lake City, UT, was one of the first to combine pipe rammers with augers on a consistent basis. His success and failures formed the benchmark upon which other contractors base their opinion of this unconventional arrangement.
For Helm, it wasn't an "either or" proposition. His successful business already owned several augers, but there were job-site circumstances that warranted an investment in pipe ramming. Helm's crews often encountered soil conditions where augers were not efficient or effective. These soils generally had a high content of rock and cobble.
Instead of displacing soil, pipe rammers simply insert casings into the ground. It's the same basic premise as sticking a drinking straw into a chocolate chip shake. At this point, there is substance both inside and outside the straw, or pipe. Removing the "spoils" from inside the pipe casing can be accomplished in two ways. In smaller diameter pipe, spoils are ejected by using compressed air. Augers are also used to remove the earth and rock which was "swallowed" from the inside of larger diameter casings.
Combined the two trenchless boring tools to creatively overcome obstacles and successfully accomplish difficult bores.
- Location: Boise, ID
- Contractor: North American Construction, Inc.
- Objective: Install sewer pipe beneath irrigation canal
Jack Seburn of North American Construction (NAC), based in Caldwell, ID, recently combined augers and rammers for positive results on a sanitary sewer installation in Boise, ID.
The City of Boise required that a section of sewer pipe be installed beneath an irrigation canal. The job was open to both auger drilling and open cut methods, although the latter was deemed highly undesirable.
The complexity of boring through the rock soil was made worse by the project specification that the bore be made at a 10 percent grade. By offering the auger method, Seburn was successful in providing the lowest bid. Unfortunately, the bid was still too high for the city to afford.
This bid rejection caused Seburn to consider alternatives. He recalled stories about other trenchless methods of performing bores. As he consulted friends in the construction industry, he learned about the trenchless construction method of pipe ramming.
The Trenchless Technology Center in Ruston, LA, provided Seburn with the name of several contractors who incorporate pipe ramming, including Frank Helm of Salt Lake City and Jim Bradshaw of Omaha. After his conversations with Helm and Bradshaw, he quickly realized that pipe ramming was the answer to his dilemma. Bradshaw told him of successful pipe ramming jobs in similar and worse soil conditions than what Seburn would encounter in Boise. Bradshaw also indicated that he economy of using ramming tools helped him secure several jobs.
Seburn was then put in touch with Mike Schwager, Rammer Product Specialist for TT Technologies, Inc. After some discussion and consideration, they were able to formulate a game plan.
The job involved the ramming of 200 feet of 24-inch pipe at a 10 percent uphill grade beneath the canal. This pipe would be traveling through glacial till with rock diameters of 12 inches. The 24-inch pipe would simply "swallow-up" the rock and soil that was in its path. To help accomplish this task, the first pipe section is fitted with a "cutting shoe." This beveled edge of the shoe allows the pipe to slice through the soil more efficiently. Once a section or two of pipe was installed, crews would then turn to the auger to remove the spoils from inside the casing.
Arrangements had been made with Schwager, as well as Jim Moore from TT Technologies to bring a Koloss Pipe Rammer, along with the appropriate accessories. Mark Hanson of Idaho Bit and Steel also lent his expertise to the project.
By arranging to have a rammer on a rental basis, Seburn was then able to re-estimate the installation, resulting in NAC being awarded the bid. "Originally, some of the municipality's specs wouldn't have allowed us to using ramming. But I worked with Masco (Boise, ID), the general contractor, and we were able to get a few changes made," said Seburn.
At the job site, the pipe was positioned on two 24-inch pipe cradles atop the auger track. The 0 to 40-foot lead pipe was rammed into the rocky soil in just 20 minutes. The lead pipe fit-up weld was made and the next section of pipe (40 to 80 feet) was also rammed in just 20 minutes.
At this point, it was decided that crews would auger-out the pipe and check the grade. Crews used a laser to ascertain the angle. It was determined that the grade had dropped only two inches in 80 feet, which was well within the pre-established tolerances.
The final two 40-foot sections were then installed, taking just under an hour ramming time for each pipe. The entire installation took place over four days, with just three hours of total ramming time. Referring to the general contractor and municipality's reaction to the installation, Seburn remarked, "They were pleased, happy with the time frame."
NAC then purchased a Grundoram from TT Technologies and have used it at several job sites.
Reflecting on the Boise job, Seburn said, "Augers could have created voids. That would have been a problem for this installation beneath the canal. The really good thing about the ramming tool is that it eliminated the risk of voids."
- Location: Brookfield, WI
- Contractor: Michels Pipeline Construction, Inc.
- Objective: Install casings beneath railway
What do difficult soil conditions, a high water table, exact grade requirements and sub-zero temperatures have in common? They were all present at a pipe ramming job in Wisconsin.
Michels Pipeline of Brownsville, WI, had the task of installing 180 feet of 48-inch steel casings beneath two railroad tracks near Brookfield, WI. It had been determined that the traditional method of augering would not be a good choice because of the high water table and mixed glacial till soil. In fact, boulders ranging from 16 to 20 inches in diameter peppered the earth.
Michels Pipeline's Field Superintendent Bill Weltin and staff then considered using a pipe rammer to effect the installation. They contacted TT's Schwager and Rich Prosser for suggestions.
For this installation, a Grundoram Goliath pipe rammer was selected for the 48-inch casing installation. The Goliath has a diameter of 18 inches with air consumption of 1,225 cfm. "In this area of the country, because of glacial till, the use of ramming is appropriate," said Weltin.
Once Super Excavators (Milwaukee, WI), the primary contractor, finished setting the bore shaft and de-watering the site, the Michels' crews could proceed with the installation in sub-zero cold.
Schwager helped with fabrication of a "cutting shoe," which was welded to the front of the initial casing to facilitate slicing larger diameter than the casing, a minimal void was created, usually resulting in a drop of four to 5 inches for every 100 feet of installation.
Only seven feet of the casing was rammed the first day, due to the exact requirement of the bore trajectory. The condition of soft sand in the shoring box also allowed some settling of the tool which slowed efforts.
The next morning, the first section was finished and the second section of casing was welded to the back of it. In less than an hour, the second section was in. The inside of the first two casings were then augered out to remove spoils. This eliminated internal friction, which sped the subsequent installations. It also allowed crews to check the grade.
It was found that the leading pipe edge had dropped 2 1/2 inches in 40 feet. To help maintain a workable grade, Michels crews installed two concrete wings beneath the pipe by cutting from inside the casing.
It helped. Grade loss was maintained at a consistent level. Each pipe section installation was accomplished in under one hour. The entire casing installation was completed in less than 30 days from the first day of ramming. "It (rammer) successfully brought the casing across," said Weltin.
In all, the grade had dropped a total of 10 1/2 inches in 180 feet, which was deemed workable by the contractor and municipality. After spoils were removed with an auger, a new 24-inch PVC sewer pipe was secured inside the 180 feet of casing.
- Location: Bricktown, NJ
- Contractor: Northeast Construction
- Objective: Install pipe beneath four-lane highway
Yet another scenario where a pipe rammer and auger worked successfully together took place recently in New Jersey.
Northeast Construction (Lakewood, NJ) was responsible for a water pipe installation beneath the Garden State Parkway near Bricktown, NJ. Soil conditions were not ideal for auger use. The ground was primarily made up of tightly packed, extremely fine sand.
Northeast Construction's Project Manager George Gutierrez decided to contact a local machinery company to inquire about the trenchless construction method of pneumatic pipe ramming.
Gutierrez got in tough with a TT Technologies distributor, looking for information about a pipe ramming tool that could handle the installation of 100 feet of 36-inch casing. Based on information from the distributor, Gutierrez ordered a Grundoram Goliath Pipe Rammer.
Once the rammer arrived, tracks were quickly laid to support and guide the rammer and the installation of the first section of pipe was completed.
Welding crews than attached the second section, and ramming was once again underway. The next two sections of casing (20 feet each) were installed in less than an hour each. The fourth section, however, took nearly two hours to ram. Crews then decided to use their auger to remove spoils in order to alleviate the internal friction against the pipe. This would make the final casing installation faster and easier.
The final 20 foot section was installed the next working day in just 38 minutes. The casing was installed within one inch of grade.
The bottom line: Get the job done. And get it done quickly, effectively and profitably. The contractors in this story found a way to be successful, even in seemingly overwhelming circumstances by combining tools.
Like the automobile, computer and cellular phone, pipe ramming tools faced a great amount of scrutiny upon their introduction. Now that contractors routinely combine rammers and augers with positive results, the exception is fast becoming the rule.
Pipeline & Utilities Construction, September 1996, Pages 13-14, 16