Design Considerations in Stiff Track Modulus Environments
Date
2002-02
Journal Title
Journal ISSN
Volume Title
Publisher
Railway Track & Structures Magazine
Abstract
The Alameda Corridor is a 20-mile long rail corridor that will provide improved freight access for the Union Pacific Railroad and the BNSF Railway from the Ports of Los Angeles and Long Beach to the rail yards and points east. The Mid-Corridor Trench is a 10-mile long section of the Corridor that will grade-separate the rail line from vehicular traffic via 30 new overhead bridges. The Trench is open topped, 30-feet deep and 51-feet wide. Initially it will have two main tracks although it was designed for a future third track. The general configuration of the Trench consists of three-foot diameter cast-in-drilled hole (CIDH) piles placed four feet on center. Connecting components are the shotcrete facing, cast-in-place concrete floor slab, integral top wales and precast concrete struts. See Figure A. The tracks will have 136-lb. continuous welded rail with concrete ties. The cast-in-place concrete floor slab varies in thickness from 48 inches to 12 inches depending on the water table and soil conditions. Originally, twelve inches of ballast was planned between the concrete floor and the concrete ties. Analysis of this design showed this to be a very stiff, non-resilient track modulus environment.
The initial concern was the effect the train loads would have upon the ballast in terms of accelerated degradation. However, other components of the track structure, specifically the concrete ties, rail fasteners, rail pads and the rail itself were also identified as having the potential for reduced service life and higher levels of maintenance.
Description
Keywords
Rail corridor, Track structure
Citation
Redden, J.W.P., Selig, E.T. & Zarembski, A.M., “Design Considerations in Stiff Track Modulus Environments”, Railway Track & Structures Magazine. February 2002.