TOP DOWN ROAD RECONSTRUCTION
The final product gained the necessary road width allowing for enhanced road geometrics and additional shoulder width (Figure 10).
Figure 12. Preliminary grubbing completed. Barrier and logs exposed.
Figure 10. Completed works with additional 2m of width.
Hornby Island Ford Cove Hill
Hornby Island is a remote Northern Gulf Island just south of Comox, BC. Travelling there requires two ferries from Vancouver Island, via Denman Island. This trip takes time and logistical challenges for not only the locals but construc- tion intent too.
The Island has one main access road from which the second- ary roads connect to. Near the end of this road is a large cliff escarpment of conglomerate and sedimentary rock sequences. The road traverses down across the cliff face to the harbour below.
Near the top of the hill was a section that was built out onto a rudimentary log crib and a poorly constructed road side barrier “wall”. The challenge was the logs were rotten and no longer able to support the shoulder fills above. The consequential settlement was impacting the road surface, the cross culvert system, and increased the maintenance needs.
Unlike the other sites highlighted in this paper, bottom up construction was an option. The preliminary design to remove the shoulder fills and reconstruct with GRS founded on bedrock was completed, however the construction cost estimate was more than anticipated and the need to remove the protected Gerry Oaks from the work zone was not desirable so alterna- tives were investigated.
The result of the second phase investigation found that a “beam” of soil anchors across the top of the slope would adequately support the failing shoulder fills and off-load the soil below stabilize them as well. The overall construction cost was less than half of the original design and no trees were lost in the process.
Figure 11. Hornby
Island, Ford Cove Hill pre construction.
Figure 13. Completed project using loose straw for revegetation, wire mesh facing with closely spaced soil/rock anchors.
Highway 14, Lost Creek Culvert
On August 30, 2012, the author sat in a pre construction meeting for a paving project along Highway 14 near Sombiro Bridge. During the meeting it became apparent that the can- tilevered log section in Lost Creek had not been identified or highlighted to the contractor, nor had construction plans been investigated due to the technical challenges of the site. This was a problem as it would not address the maintenance issue of the site and the contractor was reluctant to cross the area with the heavy asphalt equipment.
The 15m wide segment crossed a natural steep gully sys- tem where the bedrock quickly fell away. The cliff below was approximately 40m high above Lost Creek with an overall slope angle of nearly 60 degrees. Shoulder loss was mitigated with the addition of several logs in the fill effectively bridging the gully and twin culvert system (Figure 14).
Figure 14. Highway 14, Lost Creek Pre Construction.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64