The City of Fort Collins (Colorado) recently completed construction of a tunnel underneath BNSF Railway tracks to connect more than 30 miles of trails. The prospect of tunneling under an active rail line is a pretty big deal, and the railroad had strict requirements. The original concept of the tunnel was modified by the contractor and their engineer to utilize secant pile retaining walls to allow the construction of the portals closer to the rail line and decreasing the overall tunnel length. The tunnel was constructed by BT Construction and Lithos Engineering was their design engineer. Yenter construction was responsible for the retaining walls, including segments of sheet pile wall used to start things off. Anderson Drilling constructed the shafts for the secant pile wall and for the thrust wall. Read more about the project at TBM.
A stretch of tunnel on Eastbound I-70 in scenic Glenwood Canyon Colorado was closed last March because of a 70-foot long crack in the ceiling. Since then the two-lane westbound bore has been handling both eastbound and westbound traffic while repairs to the damaged segment were undertaken. This project has a little of everything: heavy excavation, rockfall, slab reinforcing, geofoam, and even geogrid! Read on for more details, a map and photos. (Photo by Concrete Works Of Colorado)
In the mountains of Peru a tunnel-boring machine named â€œPacha Mamaâ€ is grinding through the heart of the Andes under rock as deep as 6,890 ft. It is carving away at a 20.2-kilometer-long tunnel through the South American Continental Divide to deliver water to arid coastal farmland.
This is a really interesting project, known as the Los Olmos project, and a nice little article. Normally for a civil tunnel project you drill geotechnical holes beforehand to know what kind of material you’re dealing with. In this case, because of the depth, they don’t have that luxury, so all decisions will be made on the fly. The depth of the tunnel creates some very challenging rock mechanics and logistics problems as well! (Illustration by Odebrecht)