|
Event
AEG SoCal April 5, 2022 Meeting
Date: Tuesday, April 5, 2022
Time: 5:45pm
Place: Victorio's Ristorante
Speaker: Dean Francuch, Shannon & Wilson
Topic: BNSF Railway Southern Transcon Mainline Dual Track Bridge Replacement over the Mojave River, Victorville, California
The Burlington Northern Santa Fe (BNSF) Railway needed to replace two aging steel truss bridges on their southern Transcon mainline. The bridges, built in 1886 and 1923, which carry approximately 80 trains a day, required upgrading to handle heavier and more frequent loads. They were also plagued with static electricity discharge from low-hanging high-tension wires from Los Angeles Department Water and Power electrical transmission lines. The static electricity affected maintenance on the bridge, as railway workers would receive electrical shocks while working on the bridge superstructure. The new bridge would be a two track at-grade combination concrete and steel structure, with foundations and abutments designed to carry a future 3rd track. Additionally, approximately 2000 feet of track would need to be realigned, which required 700 linear feet of new cuts up to 40 feet high, in granitic bedrock.
Geologic and environmental conditions for the bridge included foundation excavation into shallow granitic bedrock, subsurface delineation between granitic boulders vs. in-place bedrock, and exploration constrained by frequent train traffic and access to either side of the bridge over the Mojave River, which has year-round water flow in this location due to the shallow bedrock. Exploration techniques included both continuous core drilling in the abutment areas, and test pits within the river alluvium. For the cut slopes, a detailed mapping program was completed to determine potential daylighted joints.
Starting in November 2019, construction of the new railroad bridge required erection of a temporary access span on the west side of the existing railroad bridge for cranes and equipment used to build the new bridge as well as disassemble the existing bridges. Access road construction to the temporary bridge required the stabilization of the existing tracks, building a 10 foot high retaining wall with a series of rock bolts drilled below the existing tracks while trains were running. The new bridge required a central pier founded in the granitic bedrock below the river channel alluvium. Because of the uncertainty of the alluvium-bedrock contact, specialized drilling techniques, as well as full-time geologic observation were required to assure that the pier was founded in bedrock and not on alluvial boulders. Explosives were used to create the new cuts in granite on the east side of the new alignment. Careful planning was required during blasting to ensure that the adjacent active track was undisturbed. The new bridge was completed and opened to train traffic in March 2021.
|
|
 |
LocationVictorio's Ristorante
10901 Victory Blvd.
North Hollywood, CA 91606
United States
Categories
| Kid Friendly: No |
| Dog Friendly: No |
| Non-Smoking: Yes! |
| Wheelchair Accessible: Yes! |
|
Contact
|
