Olson Construction Law

road construction lawyers

Trenchless Technology: Microtunneling and its use in road construction projects

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Trenchless Technology: Microtunneling and its use in road construction projects

Microtunneling is a trenchless technology that is a subcategory of the traditional Jack and Bore method with a couple significant differences.

While microtunneling still utilizes pipe jacking fundamentals, it is typically remote controlled and requires no personnel entry into the bore path. Further, Microtunneling provides continuous support to the excavation face via a fluid-based slurry, along with a spoil removal system. This support system also controls erosion at the point of the tunnel face, which can be a primary cause of undesired surface settlement. Due to the presence of microtunneling’s closed system and specialized cutting face, microtunneling is unable to handle soils with cobbles, boulders or obstructions > 4 inches, but the same features make it well suited for soft or wet soils.

Early engagement of a licensed attorney is recommended if changed conditions are encountered during the performance of microtunneling work. 

See OCL’s May 1, 2019 Blog Post for a description of Jack and Bore method.

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Trenchless Technology: Pipe Ramming and its uses in road construction projects.

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Trenchless Technology: Pipe Ramming and its uses in road construction projects.

Pipe ramming (pipe hammering or pipe jacking) utilizes pneumatic percussive blows to drive pipe through and into the ground with a pneumatic hammer.

Pipe ramming can be generally described as follows:

First, a starting point and end point are identified and marked, and a shaft or a pit (launch pit, entry pit, drive pit, or drive shaft) is constructed at the starting point. Next, a steel leading-edge band for reinforcement is attached to the leading edge of the front casing. The front casing is then placed in the drive pit, supported by adjustable bearing stands, launch cradles and platform, I-beams, or pipe jacking/auger boring machine tracks, and adjusted to achieve the desired line and grade. The pneumatic hammer or pipe ram device is then attached using collets (or special adapters) to the pipe or casing, and connected to a pneumatic or hydraulic power source, such as an air compressor. Ramming cones can be used with larger pipes to increase the amount of energy transferred between the pneumatic hammer and the pipe. Finally, the driving begins, and continues until the pipe reaches the exit point (exit pit or reception pit).  If additional segments of pipe are required, then after each segment is installed, the hammer is removed and additional segments are welded to the last installed pipe. After the full length of the pipe is installed, the casing is cleaned out, the equipment is removed, and the area is restored.

Typically, pipe ramming is used for shallow and/or short installations, such as under roads and railroads. This method is generally more suitable for preventing heave and settlement of the ground surface than other trenchless technologies. In addition, pipe ramming equipment is typically more versatile as it can operate in tight spaces and often weighs much less than auger boring or directional drilling equipment. Pipe ramming is well suited for projects with relatively short runs in soils with loose rock, or extremely fine sands. This is one of the benefits of a pipe ramming as such soils might frustrate augers or drilling heads used in the other trenchless technologies.

Early engagement of a licensed attorney is recommended if changed conditions are encountered during the performance of pipe ramming.

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What is “Jack and Bore” trenchless technology and when should it be used on road construction projects?

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What is “Jack and Bore” trenchless technology and when should it be used on road construction projects?

Jack and Bore or “Horizontal Auger Boring” (“HAB”) is one of the oldest and most widely used trenchless technologies used for installing steel pipes and casings underground.

HAB can be generally described as follows:

First, a starting point and end point for the pipe or casing are located. Next, a pit large enough to fit the HAB equipment is dug at the starting point (the “entrance pit,” “drive pit,” or “main shaft”), and a pit large enough to effectively work is dug at the end point (the “exit pit” or “reception pit”). Then, the HAB equipment is placed into the entrance pit. Next, a cutting head is attached to the lead auger and then inserted inside the front casing. The front casing is then loaded onto the equipment in the entrance pit.

Once the equipment is in place, the cutting head cuts through the soil causing the soil to fall into the casing onto the auger. The auger then draws the soil along its coils as it rotates. Once the soil reaches the entrance pit (now “spoil”), it can be removed manually, by a conveyor, or with other mechanical equipment. The jacking equipment is used to supply the force necessary to drive the casings through the ground while the cutting head is penetrating further along its course. Driving the casings while the auger is removing the soil helps prevent the soils from collapsing.

Because spoil is removed (rather than simply displaced) as it is bored, Jack and Bore may be a contractor’s best option when surface heave is a primary concern. HAB is well suited for medium stiff clays and silts all the way up to hard clays and some highly weathered shales. HAB is also well suited for medium to dense sands above the water table, and gravels with cobbles less than 4 in. in diameter.

Early engagement of a licensed attorney is recommended if changed conditions are encountered during the performance of HAB work.

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What are the most common types of trenchless technology used in road construction projects today?

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What are the most common types of trenchless technology used in road construction projects today?

Trenchless technology usage is growing throughout the country.  This will necessarily continue as more land surfaces are paved and additional vertical structures are built.

In fact, at this point in the development of the trenchless technology industry, some utility companies now presume that a trenchless technique will be utilized, as opposed to the open-cut techniques, when there is a no-dig alternative available (especially in roads).

Trenchless technology is a set of techniques for utility line installation, replacement, rehabilitation, renovation, repair, inspection, location and leak detection, with minimum excavation from the ground surface. As the industry has matured, various forms of trenchless boring and tunneling have developed. Some of the most common trenchless technologies include:

  • Horizontal Auger Boring, or, “Jack and Bore.”
  • Pipe Ramming.
  • Horizontal Directional Drilling or “HDD”.
  • Microtunneling.

Each of these trenchless technologies has its own applications and relative strengths and weaknesses. Soil type, project area sensitivity, space requirement, dig depth and bore path length may all determine which technology is best suited to a particular project. The detail and clarity of standard contract specifications for these relatively new technologies can vary from Owner to Owner. It is imperative that Contractors utilizing these technologies understand the applicable contract specifications and, in particular, the procedural requirements that must be followed in order to receive compensation when an issue with the specified technique arises. Consult a licensed attorney to review your contracts on road construction projects to ensure your work is properly compensated.

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