CSX Railroad Bridge Replacements

This paper will discuss the geotechnical aspects of foundation design, construction support, and the team work necessary to replace and upgrade 14 bridges along an existing, trafficked rail line through Central Illinois. Seven bridges were constructed using previously completed designs and seven bridges were constructed using a multi-disciplinary design-build approach. The geotechnical team provided construction support for the Phase I bridges while concurrently conducting geotechnical investigations and developing design criteria for the Phase II bridges. The project also involved many logistical considerations including minimizing bridge “out of service time” to less than ten hours for the construction of each bridge, a very tight design and construction schedule, and challenging soil conditions. The geotechnical engineering tasks associated with each Phase II bridge included: conducting subsurface investigations; performing deep foundation analyses and developing site specific design criteria; and supporting preparation of the foundation design drawings, specifications, and estimated material quantities. Design development was an iterative teamwork exercise involving the geotechnical, structural, and hydraulic engineers working jointly with the construction team. As the hydraulic and structural analyses progressed, the input parameters for the foundation design changed requiring modifications to the geotechnical design. The design process was also influenced by construction observations during Phase I of the project. These observations provided valuable installation data for the geotechnical design to provide a more cost effective and efficient design for the Phase II bridges