Bridges

Extensions of existing RE (reinforced earth) bridge abutment walls to allow for bridge widening or bridge duplication are difficult because of the need to maintain uninterrupted traffic flow whilst sections of the existing bridge abutment walls and embankments are removed.A system which provides temporary support of the bridge structure whilst allowing for the staged removal and replacement of exiting RE wall sections to support the new section of bridge or bridge extensions was developed by The Reinforced Earth Company (RECO) and Menard Bachy. This system was recently used on a number of bridge extensions on the Southern Expressway in Adelaide.The concept involved the installation of a row of jet grouted stabilised soil columns within the existing RE mass gravity volume. Their location and method of installation were specifically chosen to avoid or minimise any damage to the existing RE components that might compromise the short-term structural integrity.The final design required detailed consideration of the interaction of construction installation and bridge loading on the existing RE abutment walls as a whole. RE designers assessed the potential short-term effect of damaging existing reinforcing strips during both the initial drilling stage and during the installation of grout elements. Once the grouted columns are completed, these sections of retaining wall will behave as a weakly cemented mass gravity structure, allowing for the staged removal of existing wall sections without affecting the stability of the bridge and embankment.This paper describes this new bridge widening method, explains the required construction stages and shows the application of the system in a recent project.