A foundation underpinning system was required to provide additional support to reduce and control the culvert deformation. This paper presents the process and outcome of the geotechnical analysis of culvert deformation due to the surrounding ground movement without and with jet grout columns. The paper also outlines the effective use of jet grout columns to strengthen the foundation and control deformation.
Prior to the upgrade of Warringah Mall, a shopping centre located in the Brookvale NSW, a 4-cell box culvert located below the Condamine Street has been providing a passage for the Brookvale Creek which facilitated drainage from the centre and its vicinity to the southeast. As part of the upgrade, the two middle cells were to be deepened by 1 m while other sections of the culvert were to be retained with a design life of 50 years. The culvert was built in the mid of 1970s and crosses Condamine Street at a skew angle of about 71° to the road alignment.