Graham Residence

Residential Shoring: Complex Design Requires Innovation

A retaining wall was required to accommodate the architectural design for a private residence. The site topography presented the General Contractor (Builder) with the challenging task of constructing a retaining wall structure into a steep hill on a residential lot in the Mount Royal area of Calgary, Alberta. To accommodate the residence, extensive shoring was required along the property lines and the back alley of the site.

The retaining wall was designed by T.H. O’Rourke Structural Consultants Inc. as a Tied-back Shotcrete Shoring Wall with its excavation depths ranging from between 6.0m to 12.0m below-grade.
The length of the shoring wall is approximately 87.0 lin. metres with a total of 382 square metres of exposed surface area. The shoring design also reflects the structural Engineer’s requirement for a permanent retaining wall at the back of the property (deepest excavation).
In addition, the client accepted HCM’s proposal to provide monitoring of the permanent wall, which included the supply and installation of inclinometers and their subsequent reading for the duration of one year.
HCM completed the soil nailing operations with a TEI drill mounted on an excavator hoe.
The project required precision in placing the shotcrete shoring along the contour of the building envelope as a significant amount of the shoring was adjacent to the property’s steep slope.
Also, special emphasis was put on the sensitivity of the entire project with respect to neighboring properties, minimizing disruption, noise and vibrations to existing structures.

HCM Contractors finished this project on schedule and to the complete satisfaction of the Builder and Owner.

Client: Wiens and Company
Location: Calgary, Alberta

EEEL University of Calgary

Zero Ground Loss

This project followed shortly after finishing the Taylor Family Digital Library project, which was in close proximity to this site on the same campus. Design considerations for the foundations were almost identical to the previous project, with the installation of approximately 175 cast-in-place belled piles. Again, this new building was a result of the fast-growing population at the University of Calgary and the demand for specialty studies with emphasis on future global trends such as clean energy and the environment.

The soil conditions, which are typical and uniform throughout the mentioned site, consisted mainly of silty sand and clay till which is ideal for large capacity belled piles.

The shafts for the piles were predominantly 900mm, 1000mm, and 1,200mm in diameter.
The bells were sized at: 2000mm, 2400mm, 2800mm, 3400mm and 3600mm in diameter.

The average founding depth on this project was approximately 13.0m – 17.0m with the need to protect the upper portion of the pile shafts by using temporary casing approximately 8.0m long. The concrete volumes for single piles ranged between 23 – 26 cubic meters. Among the challenges for HCM on this project was installation of piles in close proximity to a concrete utility tunnel. EllisDon approached HCM with a request for shoring and underpinning on a portion of the tunnel.

HCM proposed a design/build tied-back continuous caisson wall method where special consideration was given to the stated goal of zero ground loss from underneath of the tunnel.

Client: EllisDon Corporation
Location: Calgary, Alberta

Centron Business Park Retaining Wall

Steep Slope Retaining Wall

The site topography presented the developer with the challenging task of constructing a permanent retaining wall structure into a hill formation near Blackfoot Trail in southeast Calgary, Alberta. The purpose of the permanent wall was to support a portion of 4th Street S.E. which is serving as an access road to a multi-building complex for commercial real estate. The retaining wall was designed by EBA Engineering Consultants Ltd. as a Cantilever Tangent Wall with various excavation depths, c/w embedment of soldier piles between 7.5m and 14.5m below-grade. The length of shoring wall was 142 linear metres with a total of 470 square metres of exposed surface area. The pile sizes included diameters of 810mm and 912mm. The overall scope of work consisted of drilling approximately 70 soldier piles and 140 filler piles. The client also accepted HCM’s proposal to trim the front surface of the 10 MPa concrete wall which then became more suitable for future application of architectural cladding or finished shotcrete. HCM completed this task with an excavator-mounted Antraquip wall trimmer.

The design also required precision in the placing of the piles along the contour of a curvilinear access road which, in most cases, took place on the edge of a steep slope.

HCM Contractors successfully completed this project to the engineer’s satisfaction, and on schedule.

Client: Centron Group of Companies
Location: Calgary, Alberta

The Bow

The future Bow building, located in Calgary, Alberta Canada, is an innovation in both architectural and shoring design. At 58 stories and with a footprint of two city blocks, The Bow will be the largest building in Canada west of Toronto. It will be an impressive addition to the Calgary skyline and will serve to redevelop the east side of Calgary’s downtown. With 850 caissons to be drilled, combined with extensive shotcrete, there will be 13,200m2 of total shoring implemented for the construction of The Bow. This is the largest shoring job of its kind in western Canada. HCM Contractors Inc. is proud to be part of the team constructing this ground breaking new building for Calgary.

For this project, Ontario based excavation-shoring, foundation specialty contractor HC Matcon Inc. expanded into the Alberta market as the newly incorporated company HCM Contractors Inc. A new team was formed to build HCM Contractors Inc. from both experienced HC Matcon Inc. employees and new hires. Now based in Calgary, HCM Contractors Inc. brings with it the expertise that has made HC Matcon Inc. respected in the Ontario specialty shoring market.

HCM Contractors Inc. has invested heavily in new equipment for this shoring project. With the purchase of two new state of the art piling drills, the Bauer BG2 24 and Casagrande B250, HCM Contractors Inc. has risen to the forefront of caisson drilling in Calgary. The two machines allow HCM Contractors Inc. to handle jobs of impressive size. Purchases include a two Casagrande M9 drills for drilling tiebacks as well as additional foundation equipment.

With design from Toronto based Isherwood Associates, HCM Contractors Inc. is introducing the Berlin wall method of shoring to the Calgary construction market. The Berlin wall method involves a combination of caisson wall and shotcrete. The soil conditions in Calgary are unique due to the city’s glaciated geological history. The soil is composed mainly of gravel and cobbles– transitioning to rock layers of mudstone, siltstone, and sandstone. No one shoring system is ideally suited to all layers. The Berlin wall method allows the shoring system to be tailored to the variable soil conditions of Calgary while still passing on a significant cost saving to the customer. The caisson wall, completely enclosing two city blocks, penetrates the lower rock to cut off water in the gravel and eliminates all upper ground loss, unlike what would be typical of lagging systems. At the same time, the caisson wall provides greater stiffness and controls the movement of the shoring wall. At lower depths, the rock requires less support and caissons are not needed– anchored shotcrete provides an optimal solution.

HCM Contractors Inc. is employing a full survey crew to guarantee millimeter accuracy throughout the shoring installation. Our team utilizes a total station system with targets on the bottom and top of each pile as well as on neighboring buildings. This ensures precision with the caisson layout and implementation of the shoring system. The project also includes the installation of twelve vertical inclinometers and twelve rock extensometers. This is the first time that rock extensometers have been used in construction in western Canada. These instruments provide us with sub millimeter data on movement within the shoring system. With precision monitoring of moments during excavation allows for additional anchors to be installed on an as required basis.

Client: Matthews Southwest

Location: Calgary, Alberta