This summer I was fortunate to take a journey to a friends woodland cabin. It is located in the far north and involves a drive of about 8 hrs to reach the nearby town.
This being Ontario that highway winds north through some remarkable country, to be sure. Huge rock outcrops have been blasted to smithereens to accommodate the road.
In so many spots, and the rocks they blasted through were mostly granite!
Now, I like a straight road as much as the next person, but wouldn’t it be cheaper to just go around?
I know, the old, now largely unused original routes, did just that. Making the roads all twisty and up and down and around. No doubt a little more dangerous and tricky to drive, but still motor able.
Anyone know why they do this? Is it safety? Are twisty, windy roads that dangerous that it is cost effective to do so much blasting? It must be expensive.
Don’t get me wrong, on the twisty roads the journey could have been several hours longer. And it was a beautiful multilane highway, but still. You could hardly go more than a couple of miles without driving through an area they had blasted.
Safety gets my vote. Both vertical and horizontal curves have limits now for just how much “curve” is allowed. That’s also related to the design speed - a curve which is safe at 20 mph may not be safe at 100 mph. Canadian roadway design standards probably dictate the grades and amounts of curvature used, thus requiring the rock blasting you saw.
Straighter roads are also cheaper to design, build, and maintain.
I’ve not ever worked roadway design, but what I remember from class and have picked up from fellow roadway design engineers over the years, is that the roadway alignment is the first thing to establish. There is a lot of detail involved, including going around things like cemetaries and Native American sites; deciding how to cross rivers or lakes; choosing a path which has good underlying soils; etc.
The next step is to determine the road grades. Several design elements come into play such as what grades are best to ‘balance’ the cut and fill sections, how to establish connections with existing roads, what elevations are needed to keep the road above floodplains, etc.
Basically the engineers go through a kind of optimization routine, with lots of different variables, and come up with their design.
I wonder if there is a history of the highway you traveled, which talks about the blasting necessary for the project? Our DOT does that here sometimes.
I would imagine the first comment plays a large role in explaining the blasting necessary. I’m no engineer but I’ve been through northern Ontario a few times, both by car and by train, and I noticed that the ground seemed to be either solid granite, or covered by a lake, or simply muskeg, which is boggy and often deep. Building a road on muskeg would be inadvisable because it couldn’t support a road or railbed, building bridges wherever a lake was encountered would be prohibitive given the number of lakes, and so the last alternative is going on or through the granite.
Again, I’m no engineer, but it is my understanding that modern roads have limits on grades, as well as such things as maximum/minimum turning radii; and if a lump of granite gets in the way of building the modern road within these specifications, it will be blasted. Northern Ontario has plenty of granite, so if there are to be roads, there’s going to be a lot of blasting.
Perhaps the old roads could go around the larger rocks, but more modern roads are built for more modern traffic–heavier trucks, greater speeds–that the old roads that went around might not have been able to support safely. You don’t want to have to handle an 18-wheeler at 100 km/h (approx 60 mph) on what was once an old settler’s trail where the biggest thing on it was a Model T.