HC Matcon Inc., through its partner the Matcon Group of Vancouver, has brought shotcrete shoring to the forefront in the Greater Toronto Area of Ontario.

Shotcrete shoring utilizes soil nails or soil anchors to develop a reinforced earth design, with a shotcrete spray that is all field applied. Steel reinforcing is reduced as compared to conventional shoring methods, such as soldier piles and lagging and caisson walls, so cost reduction is very real with this system.

HC Matcon Inc. is the first company in Ontario to produce shotcrete results to match the performance of Caisson walls next to buildings. The addition of vertical elements and design redundancy by HC Matcon has allowed for precision measurement of the horizontal movement control to as low as .25 of an inch on vertical excavation support of 35 Ft.

Advantages of shotcrete shoring include field flexibility with geometry, ease of tight site access due to smaller sized equipment, speed and above all, low cost.

Another key benefit is that the system is thin. Typically, developers require as much room as possible for parking spaces, and the shotcrete system can work to 6 inches from property line, provided tieback permission is achieved for nails that go beyond property line.

Technical Papers

Soil Nailing Earth Shoring System (Nadir Ansari, P.Eng). (www.isherwood.to) Soil Nailing Earth Shoring System: A Ten-Year Update (Nadir Ansari, P.Eng. & Carol Domitric, P.Eng.) (www.isherwood.to) Design, prediction and performance of tied back shotcrete walls supporting masonry hospital structures. (Frank Borda, Carol Domitric, P.Eng., and Matthew Janes, P.Eng., Isherwood Associates, Martin Halliwell, P.Eng., HC Matcon Ltd.)

The shotcrete shoring allows for immediate excavation of the site as no preliminary piling phase is needed. The reduction in large vertical drilling has reduced obstruction claims that traditional foundation contractors may be asking for on many sites with boulders or underground difficulties. Since the shoring is trimmed and advanced with an excavator, the obstruction removal is low cost.

The typical excavation sequence involves underpinning type panels that are done over several days. A typical 6 ft lift over a large site would take one week. A schedule approximation is then the height of the cut divided by 6, for weeks of duration.

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