[towerguy3]

How's the Speed Skating Oval in Richmond coming along? Was preloading successful? Any pics?

An interesting engineering challenge (and thus the need for preloading) is making sure such a huge building doesn't sink in that soft soil; the IOC requires a flatness tolerance of no more than one millimeter deviation across the entire length of the oval.

[fever]

1 mm. I wonder how they define this. The curvature of the earth would put the middle of the oval about 0.5 mm above a line between the edges.

[agrant]

I saw a bit on the news. I believe they're getting around to pouring the foundation.

My understanding is the building will still probably sink over time, even though it's been pre-loaded. So it will be fine for awhile, at least through the olympics, but then the use will change from speed skating to other sports (basketball, volleyball, a couple olympic sized hockey surfaces etc.).

[weezerfaninfreddy]

I wonder if they installed prefabricated vertical drains or did a fly-ash lime injection to decrease the plasticity of the soil. Does anyone here know how long they preloaded the site for?

[frinkprof]

1 mm. I wonder how they define this. The curvature of the earth would put the middle of the oval about 0.5 mm above a line between the edges.
They can take it into account. Their control survey would be of utmost importance. They would use precise levelling techniques and probably monitor it alot after construction. It would be a cool project to work on for me as I'm studying to become a geomatics engineer.

[renthefinn]

I wonder if they installed prefabricated vertical drains or did a fly-ash lime injection to decrease the plasticity of the soil. Does anyone here know how long they preloaded the site for?

I think the soils are mostly sands (non-plastic soils), prone to liquifaction, not positive on that, but would make sense for Richmond, I think they did some dynamic compaction and installed stone columns, as well as probably preloading of some sort. Not too sure on the details of the project, but I think I heard something about those methods being utilized.

[towerguy3]

That's something I never took into account: the curvature of the earth across the length of the Oval's ice surface would amount to about a millimeter anyways so how does that factor into allowable deviation? Can someone remind me of the formula used to calculate the curvature of the earth across a distance (L). The radius (r) of the Earth is 6377 km.

[frinkprof]

Along the curvature of the earth (distance along the ground, what you call L), mathematically is arclength. The distance from the point on the ground to a point at the centre of the earth (what you call R) is yes about 6 380 km. Then consider the angle (call it A) between two radial lines going from the centre of the earth to two points (say from one point on one end of the rink, to another on the other side).

Then L = RA.

If it is assumed that the earth is flat (which in most cases is alright over short intervals and if you don't need to be precise as you do in this scenario), then you lose a millimeter every 113 meters on that assumption. This is using the formula

h ~= L^2/2R

or length on the ground (or curve of the earth really) squared over two times the distance to the center of the earth. Here, h is the height difference from one point to another on the surface of the earth that is attributable to curvature of the earth.

So let's say that the distance from the two farthest points on the track is 250 meters, then you have to account for just about 2.4 mm due to the curvature of the earth.

Sorry for the marathon post, and if it is unclear, just let me know and I'll try to explain it better. Also, if you want a derivation of that second formula for h, I might take a stab at explaining that.

[Odnan]

How's the Speed Skating Oval in Richmond coming along? Was preloading successful? Any pics?

An interesting engineering challenge (and thus the need for preloading) is making sure such a huge building doesn't sink in that soft soil; the IOC requires a flatness tolerance of no more than one millimeter deviation across the entire length of the oval.

Last time I checked, speed skating does not occur directly ontop of concrete! :) The requirements is for the ice surface to be flat within a certain tolerance. The concrete surface underneath the ice is of no importance. It makes things much simpler that the water surface always tends to level by itself.

[ReginaGuy]

Is the oval really so big that they need to factor in the curvature of the earth?

short answer: no.

why?
1) The topography of the existing ground along the length of the oval is going to vary a lot more than a measly 2.4 mm

2) The track isn't being built directly on top of the the ground :rolleyes:

3) Geodetic Surveying (accounting for the size and shape of earth) is typically reserved for huge distances and benchmarking.. For a building this size, it would probably be less accurate to account for the curve of earth, because the earth isn't even a perfect sphere.