Construction Challenges and Quality Control and Assurance of Wet Deep Soil Mixing for an Approach Embankment of an Overbridge

Wet deep soil mixing (WDSM) ground treatment of varying lengths and spacing has been adopted to reduce total and differential settlements for a new bridge approach with widened embankments and transition zones for a railway overbridge. The work was part of a highway upgrade project within the Central Coast region of NSW, Australia. The ground improvement measures were required to mitigate potentially excessive settlement effects on both the road pavements and retaining walls for embankments constructed over deep, soft to firm clays. The construction faced a number of challenges during the installation of the WDSM columns. This paper presents a summary of the adopted WDSM design, the challenges faced and solutions adopted during the deep soil mixing. Details of the QA/QC procedures and test results are also presented. Results of instrumentation monitoring of the constructed approach embankments and retaining walls are also briefly discussed.