Geo 730: Jan. 27, Day 392: Terraced Roadcut

Looking across 199, Dana shot this photo of a roadcut leading up (or down, it looks like) to the tunnel. If the strike and dip of the Galice on that side of the road is similar to that of this side (which is by no means assured), what might look like near-horizontal bedding is actually a happenstance of the slope of the cut intersecting with the slate's foliation at an orientation that is close to strike. However, the eye-catching thing to me here is the pair of pronounced terraces, or flat berms, cut into the hillside in the middle and upper portion of the slope. This is a common practice in large cuts, and is engineered for two reasons that I know of. First, it forces removal of more mass from higher points, and thus helps prevent oversteepening, decreasing the risk of slope failure. Second, as rock weathers and breaks up, some amount of rockfalls and raveling are inevitable. The flat berms help capture a lot of that mass movement, and prevent it from reaching and obstructing the roadway.

Photo by Dana Hunter, unmodified. May 8, 2013. FlashEarth Location. Indexed.