Case Studies

Project Type
ELECTRICAL LINE
Location
CALGARY, ALBERTA, CANADA
Length / Hole Diameter
85 m (279 ft); 914 mm (36 in) diameter Steel Casing
Divisions
The Tunneling Company

SARCEE TRAIL CROSSING

COLLABORATING TO COMPLETE CROSSING

Project Summary

A high voltage power line was required to run underneath Sarcee Trail: one of Calgary’s main arteries, connecting commuters from the west end of the city to downtown and the south. The construction firm in charge of the project felt it would be beneficial to bring the civil engineering firm and The Tunneling Company together at the project’s outset to discuss the most practical and cost effective route.

The Tunneling Company supported the option that would involve the shortest distance. We would be required to hit the exit pit on the other side of the roadway, so a guided boring machine (GBM) was used.

Key Challenges

At 75 m (246 ft) of the pilot hole, we hit difficult ground. A large rock directly in the drill path caused the GBM to veer slightly off course, which affected our ability to see the LED guide. The Tunneling Company would have to complete the final 10 m without the benefit of the guidance system. This is where the operator’s skill and experience came into play. He remained confident the drill would emerge in the exit pit, despite the deviation – and proved to be correct. Both the construction contractor and utility company were extremely satisfied with The Tunneling Company’s work and the insights we contributed to the planning process. This led to an ongoing collaboration, which has resulted in six additional projects – and counting.

Services Provided

GUIDED BORING MACHINE (GBM)

TUNNEL BORING / PIPE JACKING

Tunnel Boring and Pipe Jacking Systems are used to hydraulically install underground pipelines up to 4.2 m (168 in) in OD range within strict alignment and grade tolerances. The likelihood of settling or sloughing is very low. Wheel machines are equipped with various cutter heads and sand shelves. A closed-face attachment is available for boring in unstable ground conditions. This versatile system can be easily adapted to work with any jacking pipe, in any pipe joint length. It can accommodate a wide range of pipe diameters.

Tunnel Boring Machines are used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through hard rock, sand, and almost anything in between. Tunnel diameters can range from 1 m and exceed 15 m (3 ft to 49 ft).

The Crossing Group - The Tunneling Company - Tunnel Boring - Pipe Jacking - Trenchless Construction - Tunneling - Augering, Boring & Pipe Ramming

SLIP BORING

A boring technique commonly used for installing oil & gas pipelines ranging from 51 mm to 1067 mm (2 in to 42 in) in diameter without leaving casing in the ground. Product pipe is welded to steel casings and either pushed or pulled through the ground in sections. The casing is cut off and removed, leaving just the product pipe. Maximum installation length is 150 m (492 ft).

The Crossing Group - The Tunneling Company - Slip Boring - Trenchless Construction - Tunneling - Augering, Boring & Pipe Ramming

DOWN THE HOLE HAMMER

A pneumatic hammer is attached to the inside edge of the casing. The front of the DTH breaks cobles, boulders and even solid rock into small pebbles or dust. The spoil makes its way through the hammer and into the casing, where it is removed by airway augers.

The Crossing Group - The Tunneling Company - Down The Hole Hammer - DTH - Trenchless Construction - Tunneling - Augering, Boring & Pipe Ramming

GUIDED BORING

A Guided Boring Machine (GBM) is used to install 305 mm to 3.6 m diameter pipe (12 in to 144 in) with grade and alignment precision. It is commonly used for installations 50 m to 150 m in length (164 ft to 492 ft) or when line and grade accuracy is critical in displaceable soil. Our GBM is extremely versatile and our customers continually approach us with new applications.

The pipe installation involves a two-step process where launch and reception shafts are strategically located to minimize surface disruption. A pilot tube with a theodolite guidance system is then pushed through the ground at the precise grade and alignment specified in the design into the reception shaft. A reaming head is welded to the pilot tube and the casing and the pilot tube is used as a guide to install casing. The GBM can be used in conjunction with auger boring or pipe ramming methodologies.

The Crossing Group - The Tunneling Company - Guided Boring - Trenchless Construction - Tunneling - Augering, Boring & Pipe Ramming

PNEUMATIC PIPE RAMMING

Pipe Ramming is used in a wide variety of soil types including gravel, cobble or sand. A pneumatic hammer is attached to the back of the casing pipe and driven through the material at any angle: from horizontal to vertical. The material is cleaned out of the pipe using an auger boring machine. Pipe Ramming methods are used for pipe diameters of 305 mm to 3.6 m (12 in to 144 in).

The Crossing Group - The Tunneling Company - Pneumatic Pipe Ramming - Tunneling - Augering, Boring & Pipe Ramming