Article submitted by Austral Masonry, an Industry Engagement Partner of Engineers Australia.
Retaining structures are one of the highest risk activities in geotechnical engineering.
We talk to international expert, Dr Chris Haberfield to find out what the common mistakes are in design retaining wall structures.
Dr Chris Haberfield is the Principal Geotechnical Engineer for Golder Associates. He is internationally recognised for his work on foundation structure interaction and soft, weak and weathered rock and in particular the analysis, design, laboratory and field testing, construction techniques and response of engineering works (e.g. foundations) in these materials. Dr Haberfield has published over 140 refereed papers many of them dealing with ground structure interaction problems, pile performance, retaining walls and analysis of such problems.
What are the common aspects overlooked or mistakes made in design which result in failure of retaining structures?
Haberfield: Failure of a retaining structure can range from a complete collapse to unacceptable performance (e.g. displacement, seepage) under service conditions. Common design failures include:
- an incorrect choice of the type of wall and wall drainage for the ground conditions at the site;
- insufficient consideration of temporary conditions (e.g. temporary unsupported batters) during construction of the wall;
- insufficient account of groundwater and of the impact of lowering ground water levels on the surrounding area;
- a misunderstanding of the behaviour of the ground and the interaction with the retaining wall;
- unforeseen ground conditions due to inadequate geotechnical investigation; an overly optimistic assessment of the properties of the ground; and
- a lack of (or inappropriate) assessment of global stability and retaining wall movement.
How would you recommend these issues are addressed?
Haberfield: These aspects can only be addressed by improving the knowledge of the designer and placing greater emphasis on the importance of being able to practically construct the design in a safe manner, without placing unacceptable risks on workers and the public or on nearby assets, buildings or services.
The design needs to be based on an accurate ground and groundwater model which requires an appropriate level of geotechnical investigation and testing.
The design of the retaining structure, including the construction process, must be clearly and simply documented and builders must adhere to all aspects of the design and construction process.
Designer participation and monitoring of retaining wall performance (e.g. wall displacements, groundwater drawdown) are required during construction to confirm design assumptions and design performance.
Dr Haberfield will be speaking at a webinar session on 15 November focusing on large scale retaining wall design and construction. Visit the event webpage to find out more.