New Technologies Expand Capabilities of Auger Boring

If trenchless technology in North America is in its adolescence, then it can be said that auger boring is the grandfather of all trenchless methods. While trenchless methods such as cured-in-place pipe, horizontal directional drilling and microtunneling didn’t come about until the 1970s and later, auger boring had long been an established method for installing pipe with minimal surface disruption.
FS-New-1The roots of auger boring can be traced to coal mines of West Virginia where the technology was used to excavate coal seams beginning in the 1930s (Martin and Grolewski, 2011). For the most part, the basic technology has remained the same with evolutionary improvements in safety, power and capabilities.
The North American Society for Trenchless Technology defines auger boring as “a technique for forming a bore from a drive pit to a reception pit, by means of a rotating cutting head” in which “spoil is removed back to the drive shaft by helically wound auger flights rotating in a steel casing.” Auger boring is typically used for short bores in diameters ranging up to 72 in. and beyond in a range of soil conditions.
One of the historic limitations to auger boring has been in the ability to steer. The traditional method allows for grade accuracy but limited capabilities to steer left and right. Steering the machine involved pulling the augers out and sending workers to the face to make adjustments. In the last decade, however, new methods for installing pipes on line and on grade have had an impact on the auger boring market. Specifically, the development of pilot tube or guided boring methods, which provide precise bores in displaceable soils, can be used in conjunction with auger boring to expand its capabilities.
The pilot tube or guided boring method uses theodolites or lasers in conjunction with a slant-face bit to provide tightly controlled line and grade accuracy in displaceable soil conditions. Once this initial bore is completed, conventional auger boring techniques can be used that follows the alignment of the pilot, allowing for greater accuracy.
“There has been development of the pilot tube guided boring equipment and that technology has really aided the auger boring business,” said Dan Liotti, president of Midwest Mole, a leading trenchless contractor based in Indianapolis. “Once your pilot bore is completed, you connect your leading piece of casing to pilot and that guides your bore. Now we’re able to do very long shots — 300, 400 ft — on really tight line and grade control, which really wasn’t possible before.
“It used to be that auger boring was more of an art because you’re in the pit, 200 ft away from your leading edge, and you had to rely on the feel of the machine and the thrust and push pressures. Now there is a lot more science to the technology.”
While the pilot tube or guided boring technology works well in displaceable soils, other technologies have been developed for use harder ground, including rock up to 25,000 psi, allowing auger boring technology to be used in conditions that were previously left for other methods. These technologies incorporate a cutting head instead of a slant-face bit to complete the pilot bore.
One technology using a cutterhead with rolling disc cutters expands the capabilities of auger boring further, said Arvid Veidmark, executive vice president for Specialized Services Co. (SSC), based in Phoenix. “The new technology enables us to contend with mixed soil and rock conditions that in the past we would have done by hand tunneling. It allows us to contend cobbles and small boulders intermixed wit sand, clay and caliche. It hasn’t changed the foundational process of auger boring; it has just given us the ability to apply it more broadly.”
In addition to steering capabilities, manufacturers are providing machines with more thrust and horsepower, which enable longer drives and larger diameters, said Jimmy Lee, field service technician for American Augers. “It used to be that a 200-ft bore was scary,” he said. “Now we are seeing 600-ft drives with 54-in. pipe. We did a bore of 500-ft with 84-in. pipe. We are reaching out there farther and farther.”
As with any trenchless project, proper planning is the key to success in auger boring. “Proper set up is 85 percent of the job,” Lee said. “I see a lot of problems that arise because the pit is not properly set up. Another factor is taking your time when completing the bore. It is always better in the long run to get it done right the first time.”
Soil investigations are also recommended for auger boring projects, particularly conventional auger boring, which is not conducive for crossing mixed face conditions.
Auger boring has always filled a niche within the trenchless marketplace and recent developments ensure that it will be there for some time to come. “Auger boring is a very solid, cost-effective method of installation, and the advent and incorporation of new technologies allow you to do so much more with the machines than in years past.”
Jim Rush is editor of Trenchless Technology.

AUGER BORING RIG MANUFACTURERS

Akkerman
58256 266th St.
Brownsdale, MN 55918 USA
Phone: 800-533-0386
Website: www.akkerman.com
American Augers
135 US Route 42
West Salem, OH 44287 USA
Phone: 800-324-4930
Website: www.americanaugers.com
Barbco
315 Pekin Ave SE
East Canton, OH 44730 USA
Phone: 800-448-8934
Website: www.barbco.com
Bor-It
1687 Cleveland Ave.
PO Box 789
Ashland, OH 44805 USA
Phone: 419-289-6639
Website: www.bor-it.com
Horizontal Equipment Mfg. Inc.
PO Box 5886
Pinehurst, NC 28374 USA
Phone: 800-544-9914
Website: www.horizontalholes.com
Icon Equipment Distributors Inc./Bohrtec
300 Ryders Ln.
East Brunswick, NJ 08816 USA
Phone: 800-836-5011
Website: www.iconjds.com
McLaughlin Group Inc.
2006 Perimeter Rd.
Greenville, SC 29605 USA
Phone: 800-435-9340
Website: www.mightymole.com
Michael Byrne Mfg.
1855 Earth Boring Rd.
Mansfield, OH 44903 USA
Phone: 800-613-7206
Website: www.byrnegroup.com

The Robbins Company

29100 Hall St
Solon, OH 44139 USA
Phone: 440-248-3303
Website: www.robbinstbm.com
Vermeer Corp.
1210 Vermeer Road East
Pella, IA 50219 USA
Phone: 641-628-3141
Website: www.vermeer.com

Horizontal Boring Helps Update Pioneer Village

Located just north of Phoenix off of the Interstate 17 sits Pioneer Village, a historic park that educates locals and visitors about Arizona’s history in the territorial days from 1863 to 1912. Opened in 1969 by the Arizona Pioneer Association, it has been a popular destination for field trips, serving over 1 million children. In 2010 the private association was no longer able to keep the park open and the City of Phoenix purchased it and began to make improvements to the facilities. One needed upgrade was to the utilities, including an expanded water source to the village.
FS-New-2Specialized Services Co. (SSC) was selected as the horizontal boring subcontractor by Quest Civil Ventures, the general contractor on the project. A 36-in. steel casing would have to cross from the east side of I-17 to the village on the west side to carry a 16-in. water line. I-17 carries three lanes of traffic in each direction at this location creating the need for a 400-ft bore to span the distance, one of the longest bores performed by SSC to date. To add to the challenge, the final foot of the bore on the west side of the freeway would be crossing under a main fiber optic line that serviced the nearby federal prison and a large portion of northern Arizona.
Co-owner of SSC and head of field operations, Abe Veidmark, was up for the challenge. The combination of the length, solid rock soil conditions and extremely critical line and grade made this a job that demanded his leadership and expertise. SSC was equipped to do this job having added a 36-in. Robbins SBU (Small Boring Unit) head to its equipment fleet in 2009. Prior to the use of SBUs, this job would have had to be performed using hand tunnel to contend with the rock conditions. This would have created a footage production rate of 4 ft per day, whereas the SBU was able to generate 20 ft per day.
The bore was started with the SBU and a 36/600 American Augers bore machine. After 200 ft was installed, the weight of the auger was too much for this bore machine and it was replaced with a 48/54 Barbco bore machine which offered greater horsepower to keep the auger spinning. The bore was completed on almost perfect line and grade, finishing only 2 in. to the right and 3 in. low, easily clearing the fiber-optic line and in exact location needed for the open-cut crews to tie onto. Upon conclusion of the bore, the 16-in. waterline was pushed through the steel casing by SSC on stainless steel casing spacers, connecting the historic village to its new water supply.
Article supplied by Specialized Services Co., Phoenix.
Read More

Backreaming Through Rock

Taking on a challenge is nothing out of the ordinary for the experienced trenchless installation experts at Midwest Mole. Since its founding in 1982, the Indianapolis-based contractor has earned a reputation for installation innovation, overcoming obstacles and defying the odds. So, these trenchless pros didn’t hesitate to take on another challenge despite the recognition that they would likely encounter a few unknown and unexpected twists and turns along the way.

Midwest Mole was hired by general contractor Dudley Construction on behalf of project owner Northern Kentucky Sanitation District No. 1 (SD1). SD1 is responsible for the collection and treatment of Northern Kentucky’s wastewater, as well as regional storm water management and is the second largest public sewer utility in the state. The district’s service area covers approximately 220 sq miles in three Northern Kentucky counties, serving more than 30 municipalities and several unincorporated areas. SD1 maintains more than 1,600 miles of sanitary sewer line, more than 140 wastewater pumping stations, several treatment plants and approximately 17,800 storm sewer structures.

This project, located just outside of Florence, Ky., was to install a 506-ft section of 18-in. DR11 HDPE material that would eliminate a pump station and convert the existing sewer from a forced main to gravity flow. It was to be installed at 1.3 percent grade using auger boring as the installation method. The greatest challenge, however, was neither the grade nor the material, or even restricted access to the site — which would necessitate traversing over hilly, heavily-wooded terrain — but as is often the case, it would be ground conditions posing the bigger concern. After reviewing the plan, however, Midwest Mole project manager David Howell had an idea for an alternative approach.

“This was in a residential area with a lot of trees, on a hill and very limited access,” Howell says, “and it was also solid rock. SD1 had designed it to basically be bored through the hill with the auger boring method. We had used an AXIS laser guided boring system on a project before and thought it might be a good fit here. Our only real concern was backreaming through rock.”

How It Works

The AXIS system consists of a vacuum power unit, vacuum tank and the rack power unit, along with drill casing and the drill head. Located outside the launch pit is a high-performance liquid ring vacuum power unit that removes excavated material from the bore. Upon reaching the launch pit, the excavated material transitions from the drill casing to a 6-in. diameter hose that runs up the launch pit to the vacuum tank.

Outside the pit is a self-contained power unit that features a 140-hp diesel engine and hydraulic pumps that connect to a rack (located in the launch pit) that powers rotation, thrust and pullback functions of the drill head and casing.

The operator console is designed to centralize control of multiple components into an easy-to-use interface and consists of the target display monitor, parameter display, drill head steering control, thrust/pullback control, rotation control and vacuum controls. Drill casing segments, measuring 6 1/2-ft long, are placed in the rack carriage and feature a laser sight channel and a vacuum channel for removing excavated material.

The guidance system includes a laser that determines the line and grade of the bore, enabling on-grade accuracy throughout the bore process. The drill head uses a flat-face cutter that when combined with the laser guidance system is capable of completing bores with a strict and precise degree of on-grade accuracy. In standing ground it can be retracted in mid-installation, allowing the contractor to change the cutter bit to adapt to changing soil conditions.

Eliminating a Step Helps Enhance Efficiency

The rock was composed of layered shale with veins of limestone formations ranging from 1 to 5 in. thick and measuring upward of 12,000 psi in density. The overhead power line and an existing pump station located within proximity of where the launch pit area would need to be situated were also factors. However, after verifying the location of the sewer lines currently running in and out of the pump station and sizing up the final measurements for positioning the various components of the AXIS system, Howell was confident that this laser guided boring method was indeed the best approach … and officials with SD1 concurred.

“While we agreed that it certainly would have been possible to complete the job using auger boring, we were able to identify several advantages that favored the AXIS system and presented these findings to officials at our longtime customer SD1. They weren’t all that familiar with this method, but we had worked with them on several prior projects and delighted they trusted our recommendation and gave us the green light.”

Howell cited three important factors that helped tip the scale in favor of the AXIS system, beginning with the rock. The inconsistency of the formation and the variation in limestone and shale layers make it more difficult to maintain an accurate line and grade using auger boring. According to Howell, maintaining a precise grade — often less than 1 percent — is a major advantage for AXIS since the laser guided system allows the operator to continuously monitor the boring process and make instantaneous adjustments when changes in rock density and hardness alter the path of the drill head, albeit ever so slight.

Another important advantage for the AXIS system given the rocky Northern Kentucky terrain, coupled with the smaller-diameter material that was to be installed for the Florence project, is the ability to complete it in one pass.
“Auger boring would have necessitated a two-pass approach,” Howell explains. “The casing pipe would have to be installed first, followed by the new carrier pipe threaded inside that. And likely this approach would also have required that we grout the material in place. Not so using the AXIS system, however, as the carrier pipe could be installed directly in the bore minus the steel casing. So, in essence, we eliminated a step and that equates to less time and reduced expense.”

Midwest Mole used a 13 1/2-in. tri-cone bit for the pilot bore and achieved an average production rate of 14 ft per hour through this complex compilation of rock formations. With the HDPE pipe fused and ready on the receiving end, it was time to face the unknown and begin the backreaming phase of the project.

The one unknown, however, was whether the AXIS system would be able to effectively backream through this difficult formation of limestone, shale and high-density rock, having only pulled product back through the bore on previous installations. Howell’s crew selected a 19 1/4-in. tri-cone cutter head for navigating the 506-ft bore with roller cones — a tooling configuration considered to be effective for removing rock and best positioning the reamer during pullback.

“This was the first time the AXIS system had been used to ream rock, so there was obviously some trial and error involved at first,” Howell says. “We made some adjustments along the way to get the cutter spacing set with the correct over-cut to allow the reamer to work most efficiently. We had a pulling head attached to the back side of the reamer on a swivel, which helps to clear the bore, so we were pulling the product pipe back in as the hole was reamed. We used the standard Vermeer reamer design custom built with roller cone cutting heads.”

Howell admits there were some nervous moments prior to pullback. “We knew that we had thought the project out as thoroughly as possible, but there were still some tense nerves as we approached backreaming time,” Howell says. “Vermeer was there to support us, and yes, there was nervousness doing something for the first time, but all in all things went very well. We had to make some adjustments, but at the end of the day, it actually reamed the rock quite well and we were very pleased with it. We averaged about 8 ft an hour on the backream.”

Randy Happel is a features writer for Two Rivers Marketing, Des Moines, Iowa.
Read More