Support for Elevated Rail Lines

In order to accommodate increased rail traffic, rail lines were elevated in the Central Corridor route through Wichita, Kansas. This article describes some of the challenges posed to this elevation project due to the soil conditions. The project extended for three miles through areas with tight right-of-way limits, thereby requiring the use of retaining walls to support the elevated tracks. Elevating the tracks required four phases of construction that included installing more than 19,000 linear feet of precast concrete retaining wall as high as 25 feet above grade. Phased wall construction required approximately 9,000 feet of temporary, mechanically stabilized earth retaining walls. Design bearing pressures on the foundation soils beneath the retaining walls are as high as 6,000 pounds per square foot. The site is underlain by highly variable sand and clay fill overlying irregular thicknesses of compressible silt and clay soils as deep as 27 feet. These unsuitable bearing materials are underlain by medium-dense to dense sands, underlain by shale bedrock. Because of these conditions, construction of the grade separation retaining walls on top of the uncontrolled fill and compressible silt and clay soils could result in excessive total settlements of as much as 6.5 inches. Excessive differential settlements also were expected because of the variability in the soil profile. The design team opted for the rammed aggregate pier (RAP) design-build approach as a ground improvement solution for the project. The RAP elements extended through the uncontrolled fill and compressible silt and clay layers. RAP soil reinforcing elements were installed in a grid pattern prior to construction of the retaining structures to reinforce and stiffen compressible foundation soils, to reduce the magnitude and duration of settlement, and to improve bearing capacity, global stability, and the composite shear strength of the foundation soils. The RAP soil reinforcement solution met or exceeded the project performance requirements and was a cost-effective solution for reinforcing and controlling settlement of the soft and compressible soils.

Language

  • English

Media Info

  • Media Type: Print
  • Features: Figures; Photos; Tables;
  • Pagination: pp 42-45
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 01140464
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Sep 21 2009 10:20PM