Description
This view shows the Chicago & North West Railway viaduct (Kate Shelley High Bridge) over the Des Moines River from the northwest. According to the Historic American Engineering Record, this viaduct is about 3,000 feet long, 185 feet above the Des Moines River, made of 6,196 tons of steel and has a double track. At that time, there were only three other viaducts similar to this one in the world: Pennsylvania, Texas, and Bolivia, and all were smaller than this one. According to the Historic American Engineering Record, railroad tracks need to be very solid because any sagging can cause train derailment, but the river valley was unstable because it was sand, shale, mud, and silt. The solution was to dig down 8 pneumatic caissons, each 10 feet in diameter, deep enough to reach stable sandstone bedrock, anywhere from 42 to 62 feet deep. These caissons supported the piers closest to the river, four on each side. The remaining piers were supported by shallower foundations because they supported less weight.
Source-Dependent Question
- How does this view of the viaduct help you understand how the viaduct works and how it might have been constructed?
Citation Information
"3/4 View From Northwest - Chicago & Northwestern Railroad Viaduct, Spanning Des Moines River at Chicago & Northwestern Railroad tracks, Boone, Boone County, IA," Historic American Engineering Record. Courtesy of Library of Congress