A case study of a flexible reinforced soil wall (RSW)
Dr. Kourosh Kianfar
A flexible Reinforced Soil Wall (RSW) was designed and constructed as part of the Shell Cove Boat Harbour Development project. The Shell Cove Boat Harbour development is the largest coastal residential development ever initiated by a local government authority in Australia. When complete, the boat harbour will provide a water surface of approximately 12 hectares which is approximately 30% larger than Darling Harbour. Soft soils are present within and surrounding the footprint of significant portions of the harbour. A surcharging strategy was developed and adopted for improvement of the soft soils surrounding the harbour. The original surcharge design for the northern portion of the site included a surcharge mound and a batter (about 150m long and 18m wide, with a footprint of about 2700 m2). Part of the batter was only required temporarily during construction and soft soil improvement, and part of that was a permanent section. The main requirement of the batter was to support the required temporary (about 8m high) and permanent (about 3m high) embankment fill. To eliminate the batter, a flexible Reinforced Soil Wall (RSW) was designed and constructed which comprised of the following three retaining walls over each other, which based on the existing information has been done for the first time with this arrangement:
- A Gabion wall at the based (part of permanent section of the wall)
- A reinforced wall with flexible facing over the Gabion wall (as the second permanent section of the wall)
- A Wrap-Around wall over the main reinforced wall (as the temporary section of the wall)
The height of the RSW varied between 2.5m and 5m, and its width varied between 6m and 9m. The combination of the three retaining walls was mainly to eliminate the requirement for acquiring about 2700 m2 land, however the solution had the following advantages too:
- Gabion wall:
- Providing a sustainable and reliable foundation for the sections above it
- Providing drainage at the toe and underneath of the wall
- Connecting the drainage to the underneath drainage layer
- Main reinforced wall:
- Providing a flexible permanent retaining wall over consolidating/creeping soft soils
- Providing a permanent green face aesthetically matching with the environment
- Eliminating the requirement to install any wall facing
- Tolerating differential settlements
- Adjustable at the top following completion of soft soil improvement and removal of the temporary section
- Wrap-Around Wall:
- A low-cost surcharge structure
- Easy for construction and removal following completion of soft soil improvement
About the speaker
Dr. Kourosh Kianfar Executive Technical Principal and Business Unit Manager – Geotechnics (VIC), ADE Consulting Group
Kourosh is a Chartered Professional Engineer (CPEng) and has over 28 years extensive experience in the area of Geotechnical and Civil Engineering in Australia and overseas. He has extensive analytical, numerical, and experimental experience in geotechnical engineering. Kourosh has experience in the areas of project management, ground improvement, slope stability and excavation modelling and assessment, interpretation of subsurface conditions, site investigation management, numerical modelling, assessment of soil and rock parameters for foundation design, and soft soil improvement design. Kourosh has worked as a member of design team and/or project manager on many projects, including Pacific Highway Upgrade, Albion Park Rail Bypass, Berry to Bomaderry Upgrade, Shell Cove Boat Harbour, Haywards Bay Development, and Manildra’s Packing Plant. He completed his PhD degree in geotechnical engineering in soft soil improvement via vertical drains and vacuum preloading through University of Wollongong (Australia) in 2012, and worked as a University Lecturer for about 13 years overseas, as well as tutoring different geotechnical subjects in University of Wollongong between 2007 and 2012. Kourosh is also currently an Honorary Research Academic at University of Wollongong (UOW) and University of Technology Sydney (UTS). Kourosh is currently working with ADE Consulting Group as an Executive Technical Principal and Business Unit Manager – Geotechnics (VIC).
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