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Trenchless technologies: Five methods for non-disruptive utility installation

Going trenchless means installing utilities doesn’t have to include digging up lawns and tearing up streets

By Keivan Rafie, Lead Tunnel Designer, Markham, Ontario 

When I was a kid, our driveway had to be blocked every year for some type of utility installation. Sometimes, before the first contractor finished the job and fixed the asphalt, the next contractor would start digging! This seemingly never-ending cycle would drive my whole family, not to mention all our neighbors, nuts. We all wished that all the work could have been done without always digging up our driveways. Well, today, it can be. That’s where trenchless technology comes in.

We don’t often name construction methods for what they don’t accomplish. But, when it comes to Trenchless Technology, not having to dig a trench is the whole point.

Trenchless technology is basically tunneling below the surface to install service lines like water or gas pipes, electric or telecommunication cables, without anyone noticing on the surface. This method also makes it possible to install utilities under rivers canals and other obstacles with no disruption of flow and with minimum or no damage to the environment. Trenchless methods have been used for last 50 years but, these days, with advancements in technology for excavation and guidance systems, trenchless methods are becoming more commonly used around the world when soil conditions and location permits.

The most popular trenchless technologies methods are: Horizontal Directional Drilling (HDD), Micro-tunneling, Horizontal Auger Boring (HAB), Pipe Ramming, and Pipe Jacking. Here’s a quick overview of these popular methods:

Horizontal Directional Drilling (HDD): A steerable system for the installation of pipes, conduits, and cables in a shallow arc using drilling equipment from the surface. We traditionally apply HDD to large scale crossings, such as rivers. For these applications, we initially drill a fluid-filled pilot bore, then enlarge it with a larger drilling head to the size required for the product pipe.

Microtunneling (MT): A trenchless construction method for installing pipelines by consecutively pushing the Microtunneling Tunnel Boring Machine (MTBM) through the ground using a jacking system. The MTBM is operated from a control panel, normally located on the surface. It simultaneously installs pipe as soil is being excavated and removed. If required, continuous pressure is provided to the face of the excavation to balance groundwater and earth pressure.  Balancing these pressures are necessary in soft grounds to keep tunnel structure intact during the excavation.

Horizontal Auger Boring (HAB): Forming a bore from a launch pit to a reception pit, by means of a rotating cutting head. Soil is removed back to the drive shaft by auger flights rotating in a steel casing. This method may have limited steering capability but might be more economical for short and straight drives compared to other methods.

Pipe Ramming (PR): Installing steel casing (pipe) from a launch shaft to a reception shaft utilizing the force of a percussion hammer attached to the end of the pipe. A continuous casing is pushed forward to support the excavation.

Pipe Jacking (PJ): A system of directly installing pipes by pushing the pipes hydraulically from a launch shaft so that the pipes form a continuous string in the ground. This method usually requires personnel inside the pipe to perform the excavation or soil removal process. The excavation can be performed manually or mechanically

The capabilities and reliability of trenchless techniques has expanded over recent years so much so that many applications that were unheard of just a decade ago are now possible. Experienced engineers and owners know that selection of the trenchless technique, particularly for the more complex projects, is the key for successful, safe, timely and cost effective completion.

In my next blog, I’ll look more closely at the benefits of Horizontal Directional Drilling (HDD).

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Keivan’s engineering expertise is in tunneling, mining, and ground-improvement projects. For the last 15 years, he’s worked across the globe in Asia, Australia, the Middle East, and North America. Keivan’s knowledge and experience go deep with tunneling methods, such as drill and blast, NATM, and TBM, and he is involved in all stages from design to manufacturing and construction.

We don’t often name construction methods for what they don’t accomplish. But, when it comes to Trenchless Technology, not having to dig a trench is the whole point

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