Multicrete Contracting

Bulkley Canyon Retaining Wall


Project Overview

The Bulkley Canyon Retaining Wall project, located in New Hazelton British Columbia was one of 3
retaining walls constructed in order to create a railway siding between mile 36 and mile 42 of CN Rails
Bulkley Sub. The retaining wall used pressure-grouted double corrosion-protected soil anchors (DCP
Anchors) to tie back a reinforced shotcrete wall.

Project Scope

Access Road

Multicrete Systems Incorporated (MSI) built 2 access ramps at both ends of the proposed wall location.
Injection Bore Anchors (IBO Bars) were used to support a shotcrete retaining wall along the entire length
of the access road. The shotcrete retaining wall was engineered in-house to support the weight of a 30
Kip drill rig that would later drill the DCP anchors for the main retaining wall structure. Working on the
side of a canyon, a fall protection system was needed to establish a safe working zone for site personnel
to access the retaining wall. MSI built a steel fence along the entire length of the excavated slope area as
a fall protection barrier that allowed workers to access the wall without fall protection harnesses and
lanyards. (Figure 1, 2, & 3).

Multicrete Contracting - Bulkley Canyon Retaining Wall Existing Site Conditions
Figure 1 – Existing Site Conditions
Figure 2 – TYP. Access Road Cross Section
Figure 3 – Construction of Access Ramp
Anchor Installation

6” boreholes were drilled with casing using a KLEM 806‐3g drill. DCP anchors were installed and pressure
grouted to 100 PSI. While drilling, a 2‐meter‐wide void was intercepted. Multicrete recommended
consolidating the void with cementitious grout to expedite the project schedule but the change was
denied. The project engineer advised the use of grout socks to hold the column of grout injected into
the bore holes and obtain the pull‐out capacity needed for each anchor. (Figure 4).

Figure 4 – KLEM 806‐3G Drill

After the 7‐day grout strength requirement was met, the anchors were pulled to their testing load
individually. Anchors were locked off at their design pressure once the wall was shotcrete and backfilled.

Shotcrete Wall

Shotcrete was applied to a plywood false formwork from inside the shotcrete retaining wall. The false
formwork was installed on a concrete spread footing that ran the entire length of the wall. Rebar was
installed around the soil anchors and secured to the false formwork. Shotcrete was applied to the wall in
full 8” lifts across the entire length of the wall. (Figure 5).

Figure 5 – Soil Anchor Installation
Anchor Lock Off

Once the shotcrete passed its 7‐day strength requirement, the wall was backfilled with pit run material.
Anchor head assemblies were installed on the front of the anchors and the anchors were locked off at
the specified lock-off pressure. After the anchors were all locked off, the wall was complete.

Multicrete Contracting - Bulkley Canyon Retaining Wall Anchor Lock Off

Finished Product

Multicrete Contracting - Bulkley Canyon Retaining Wall Complete
Figure 6 – Complete Wall


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