Ramming renaissance

	C.H. Nix crews used a Grundoram Goliath pneumatic pipe rammer from TT Technologies to install numerous casings at different locations along a new rail line for Utah Transit Authority.

	TT Technologies was part of a world-record pipe ram project that took place in Altoona, Iowa, which rammed a 147-inch diameter casing for a bike path under track owned by Iowa Interstate Railroad. Miller the Driller was the contractor.

	80 feet of 48-inch steel casing installed under a railroad using a 24-inch HammerHead Mole pipe rammer in Bainbridge, Pa. Soil conditions as described by a HammerHead technical specialist on site were “very hard, compact soil with large cobble.”

	Pipe ramming can be a horizontal or vertical installation as an Iowa Trenchless crew demonstrates. The crew installed a 30-inch casing at a 47-percent grade for a storm sewer. The crew hammered the pipe on line and grade. After the hammering was complete, the crew used an auger boring machine to clean the casing.

There are some issues that strike across the rail industry, no matter how large or small a railroad. One of these concerns is how to keep water away from working track. One technique, pipe ramming, is being used on railroads to install new culverts and rehab existing infrastructure in order to keep track dry and working properly.

Pipe ramming played a vital role on a 44-mile project for the Utah Transit Authority when an auger bore became stuck 40 feet into a 80-foot storm-drain bore, leaving a void and a 15-foot sinkhole between two Union Pacific tracks. An 18-inch Grundoram Goliath pipe rammer was brought in to save the day and, more importantly, complete the bore.

Pipe ramming explained

The Trenchless Technology Center at Louisiana Tech University describes pipe ramming as “a trenchless method for installation of steel pipes or casings, in which a pneumatic tool is used to hammer the pipe or casing into the ground, while the excess soil from creating the borehole is removed to the surface.”

The front of the lead casing is welded with a cutting shoe to help reduce friction and cut through the soil. Bentonite or polymer lubrication can also be used to help reduce friction during ramming operations.

Steel casing sizes range from four-inches to a world-record 147 inches, depending on the project. The most common sizes are between 24 and 60 inches.

“Several options are available for ramming various lengths of pipe. An entire length of pipe can be installed at once or, for longer runs, one section at a time can be installed. In that case, the ramming tool is removed after each section is in place and a new section is welded on to the end of the newly-installed section,” said Dave Holcomb, product specialist at TT Technologies, Inc. “The ramming tool is connected to the new section and ramming continues. Depending on the size of the installation, spoil from inside the casing can be removed with compressed air, water, an augering system or other types of earthmoving equipment.”

Eric Nicholson, director of global and key accounts for HammerHead Mole, has seen a variety of methods used to clean out the casing. “People have used water jets, hydro-excavators, auger machines and, in some large installations, a mini bobcat was used to drive in and out.”

Although typical pipe rams are short and shallow, between 100 and 150 feet long and 20 feet deep or shallower, Nicholson notes that anything can be accomplished with proper preparation.

“The combination of both depth and length become contributing factors. If someone is looking at a 42 -inch pipe ram, 350-feet long, 20-feet in the ground, the combining factors make the project very difficult. You are dealing with 20 feet of earth above the casing that creates load throughout the ramming process, in conjunction with a significant length of pipe,” said Nicholson. “It’s important the extra time and preparation required to complete a project of this magnitude be fully utilized such as laser site, additional pit preparation, which may include pouring a concrete pad, additional lubrication or bentonite lines, and back up air compressor(s) to ensure any potential down time is minimized. Unlike some other trenchless methods, there is no steering capability with pipe ramming. It is critical that the first 10 to 15 feet of the casing go into the ground as perfect as possible because that will have great impact on the overall success and accuracy of the project.”

Although pipe ramming is used primarily for horizontal applications, it can be used for vertical installations such as pile driving or micro-piling.

According to Nicholson, in order to have a successful vertical ram, a device or structure is needed to hold and lift the pneumatic hammer at the proper height and angle.

Ground conditions matter

Ground conditions are a big factor when considering whether or not a project would benefit from pipe ramming.

“Pipe ramming can be used in any soil type, but the method excels in mixed-face materials and granular soils that can cause problems for boring techniques that utilize rotational soil removal methods,” said Holcomb”

Nicholson agrees, “Pipe ramming will stand out in running soil and cobble, clay is a 50-50 toss up [between ramming or auger boring] and heavy encrusted rock situations are where an auger will have a benefit because I can’t drive a steel casing straight through rock.”

Jason Clark, president of Iowa Trenchless, is currently using the process based on ground conditions. “We’re ramming in Bark River, Mich., and the ground would not allow us to do anything but ram because it’s unconsolidated material,” said Clark.

Advantages

According to The Trenchless Technology Center, pipe ramming can save both installation time and costs under favorable conditions, when compared to other trenchless methods.

“Some casing installation methods are impaired or even rendered inoperable by rock- or boulder-filled soils,” said Holcomb. “Pipe ramming is different. During pipe ramming, boulders and rocks as large as the casing itself can be ‘swallowed up’ as the casing moves through the soil and can be removed after the installation is complete. This means that there will be no undermining of the tracks regardless of the type of soil encountered. Additional advantages include no requirement for a back abutment to push against, the ability to use casing lengths of any length up to and including 150 feet, the capability to ram a larger casing over top of an existing culvert and then remove the old culvert from inside the new casing.”

For Clark, the key advantage is reducing ground loss. “When you bore you can lose ground, but when you’re pipe ramming you can’t.”

“One of the distinct advantages would be speed; you can typically insert the casing much more quickly because one of the factors with auger boring is that they are removing the soil as they make the bore,” said Nicholson. “The ability to go through certain soils that auger bores can not go through is certainly an advantage. Typically, you’re dealing with running soil, if you’re removing soil as you go, it’s hard to know if you’re creating a void.”

Nicholson, Clark and Holcomb all agree that humps, sags and voids are not strong concerns with pipe ramming.

“We’ve had a lot better luck with ramming more than anything else with having less humps and sags,” said Clark. “We’re doing an 84-inch ram that was designed with inadequate cover and it’s in looser ground, but humps and sags have not been a problem.”

Nicholson said, “This is where the ability to swallow debris is beneficial. We’re dealing with a casing that is typically a half-inch thick in diameter. If we capped off the end of the pipe and were trying to drive it into the ground, we would have a problem, but by leaving the end of the casing open, we’re allowing that debris, material, rock, railroad tie or whatever has been buried to be swallowed in the casing.”

Railroad use rising

“Railroads are purchasing ramming tools and replacing bad culverts themselves and also contract many projects out to contractors that specialize in boring. Many railroads specify ramming as a preferred boring technique after they experience the method because it minimizes the chance for undermining of the tracks,” said Holcomb.

Nicholson relates the safety factor of pipe ramming to its growing use among railroads. “It does go back to the one disadvantage of auger boring, which is that lead head is out in front of the pipe and settlement and rail safety is always a concern, so knowing that soil will not be removed until after the fact creates a great opportunity.

“It is a viable option for new installations and certainly [an option] as railroads continue to rehabilitate or continue to improve the state of their infrastructure,” said Nicholson. Clark agrees, “Railroads have been more open and we’ve been doing more of it. Some railroad people are skeptical until they see the process. We’ve never had anyone who did not like pipe ramming after using it.”