Rock Anchors and Moving Mountains

Large Block Systems, Monster Walls
By Joseph Kowalski
Oct 27, 2009 - 11:22:36 AM

Site developers in St. John, New Brunswick, Canada had BIG plans when they decided to move this mountain!  Not only would they literally have to move a small mountain, they would also have to create two walls totalling 425 meters (1,400 feet) long and up to 7 meters (23 feet) high, with very steep slopes above.

Construction began by removing large quantities of rock and exposing the bedrock surface.

It continued by constructing cast-in-place concrete footings on the cleaned bedrock.

The concrete was tested during placement, and the surface of the footing was leveled to prepare for placement of the very large blocks. 

These blocks are huge, but the size of the project makes them look small.  These blocks are actually 0.6 meters (2 feet) high and weigh a few thousand pounds each!

The rock surface was compacted and made smooth prior to geogrid placement.  At some locations, "intermediate" layers of geogrid were installed mid-height along the blocks to reduce the connection load of the geogrids above.

Connection load is the force between the geogrid and the block to which it is connected.

Near the end of the project, it was apparent that some rock simply could not be excavated.  So, we put our heads together and determined that anchoring to the bedrock would be a safe and cost-effective method to secure the bottom of the wall above Retail Drive, many feet below the base of the wall.

PDF showing rock anchors for Costco, St. John's, NB, Canada
The dowel anchor rods are shown in this drawing.  The dowel anchors were installed every 1.1 meter (4 feet) along a stretch of wall.  The anchors were made at about 45 degrees into the rock.