Pipe Ramming Provides Water Main Installation Solutions in El Paso

Utility contractor DH Underground of Albuquerque, N.M., recently installed aseries of large diameter water mains in the City of El Paso, Texas. Theinstallations were completed as part of a large-scale water system improvementplan.

In order to facilitate the installation of the water main, DH crews wouldneed to install a series of large diameter steel casings. According to DHUnderground’s Tim Kuzior, his crews utilized an assortment of trenchlessequipment to complete the installations.

“We anticipated a simple trenchless auger boring project, but plans changedonce we encountered the soil conditions,” Kuzior said. “We decided to auger borefor the first pipe section because the ground was clay, but when we got to thesecond site, the soil conditions had changed dramatically to running ‘sugar’sand. We decided that pneumatic pipe ramming would allow us to place the pipewithout slumping the road and help overcome the sandy soils. The soil was alittle better for the third installation and we used a TBM there.”

The project included installation of one 54-in. diameter, 100-ft long steelcasing through auger boring, a 58-in. diameter, 200-ft long casing throughtunnel boring and a 54-in., 160-ft long casing through pneumatic pipe ramming.Once installed, the steel casings would house a new 36-in. concrete water main.For the ram, Kuzior used its 18-in. Grundoram pipe ramming system from TTTechnologies, Aurora, Ill.

Ramming Basics & Benefits
Trenchlesspipe installation through ramming is simple; a pneumatic hammer is attached tothe rear of the casing or pipe. The ramming tool, which is basically an encasedpiston, drives the pipe through the ground with repeated percussive blows. Acutting shoe is often welded to the front of the lead casing to help reducefriction and cut through the soil. Bentonite or polymer lubrication can also beused to help reduce friction during ramming operations.

According to TT Technologies pipe ramming specialist Rick Melvin, severaloptions are available for ramming various lengths of pipe. “An entire length ofpipe can be installed at once or, for longer runs, one section at a time can beinstalled,” he said. “In that case, the ramming tool is removed after eachsection is in place and a new section is welded on to the end of the newlyinstalled section. The ramming tool is connected to the new section and rammingcontinues. Depending on the size of the installation, spoil from inside thecasing can be removed with compressed air, water, an augering system or with amini backhoe.”

Some casing installation methods are impaired or even rendered inoperable byrock or boulder filled soils. Pipe ramming is different. During pipe ramming,boulders and rocks as large as the casing itself can be “swallowed up” as thecasing moves through the soil and can be removed after the installation iscomplete.

Ramming tools are capable of installing 4- to 100-in. diameter pipe and steelcasings. Diameters up to 148 in. have been successfully installed using largescale ramming equipment. Ramming requires minimal working depths and is proveneffective for horizontal, vertical and angled applications. Ramming is alsoideal for installations under roads and rail lines because it displaces the soilwithout creating voids or slumps, which was key in the El Paso project.

“Whenever you’re installing a casing under a roadway or railway, slumps orvoids are always a concern,” Melvin said. “With the sandy soils that the DHcrews encountered in El Paso, ramming was a good choice for that installation.”

El Paso Project
The pipe ramming projecttook place underneath a highly traveled Department of Transportation road on thenortheastern side of the City of El Paso. Prior to ramming, the crew prepared alaunch area for ramming operations to take place.
“We prepped the ground atthe launch area, graded it and laid down 1-in. thick steel platforms,” Kuziorexplained. “We designed the platforms specifically for ramming. They have angleirons welded to them to support the pipe, so once they’re in place, we’re readyto go.”

After the platforms were placed, the first section of casing was moved intoposition. The DH crew then began assembling the ramming gear to connect the18-in. diameter Grundoram Goliath pipe ramming tool with the 54-in. diametercasing.
The Grundoram Goliath weighs approximately 5,400 lbs and operates at1,236 cfm. At full force, the Goliath’s piston moves at 180 strokes per minute.A pneumatically powered adjustable bearing stand was used to raise the tool tothe required height for ramming.

In order to connect the ramming tool with the casing, a series of tapered andsegmented cones are used. The configuration for the El Paso project included asegmented ram cone, as well as a soil removal cone.

“When assembled, the segmented ram cone assembly reduces the overall diameterfrom 54 in. to approximately 42 in.,” Melvin said. “The soil removal cone isthen added and further reduces the diameter to approximately 18 in. At thispoint, the tool is connected, friction fit, to the soil removal cone completingthe assembly.”

Pipe Ramming Success
Once the connectionbetween tool and casing was complete, the crew was ready to begin ramming. TheDH crew pumped several hundred gallons of bentonite and water during the rammingproject. Once a 20-ft section of casing was installed, the tool was removed andthe next section was positioned and welded to the end of the recently installedcasing. The tool was then connected to the next segment of casing and rammingbegan again.

“We made excellent progress on the ram until the 100-ft mark. At that pointthings started to slow down because of the pipe drag,” Kuzior said. “We decidedto auger out the spoil with a 54-in. auger. Once we did that, we were able toram in the remaining 60 ft without a problem. Once the entire casing wasinstalled, we augered out the rest of the spoil and began insertion of the36-in. diameter water main.”

Overall, Kuzior was impressed by the equipment performance. “It was greatproject. It really shows how versatile you need to be in this business,” hesaid. “Soil conditions can change quickly down here and you have to be preparedfor anything. It’s good to have an assortment of tools in the toolbox.”

Jim Schill is a technical writer, based in Mankato, Minn.