The reliable data that a topographic survey provides enables informed decisions to help manage risk and reduce construction time and cost.

A poor topographic survey can lead to an overly conservative approach in assessing the effect of ground improvement works - causing unnecessary costs and delays to a project. Topographic survey can deliver significant benefits to property and transport infrastructure projects.

There’s a lack of appreciation for the value of good topographic survey information and what it can be used for. Contractors often consider it an unnecessary cost, and its importance is only realised when poor data is received or when there is conflicting information about ground performance or movement.

20141218Recognising the value of topographic surveysContentFigCv2Why perform a topographic survey?

With close collaboration between the geotechnical engineer, client and professional surveyors, an accurate topographic survey can be recorded and used as a tool to assist in assessing, refining and delivering ground improvement projects in complex geotechnical conditions. When a survey is done in a precise and systematic manner, it can be used to accurately map the global response of the subsurface profile to ground improvement. 

Most importantly it will reduce the time and costs of the various ground improvement techniques.

By quantifying the ground response to dynamic compaction for uncontrolled fill sites, it’s possible to delineate the areas requiring a large amount of compaction and those that do not – saving a significant amount of money and time.

Where a preload system is used to consolidate soft clays, a survey control and recording process established early in the program allows efficient assessment of the rate of consolidation occurring during the preload.

Surveys can assist in developing controls and recording processes that allow accurate and efficient data acquisition. This then enables the assessment of the effects of ground improvement techniques and more refined solutions. 

It’s possible to develop systems that reduce assessment time and allow works to be done more efficiently.

Topographic survey is also a useful way to present meaningful information on complex geotechnical issues to a broad range of stakeholders - no matter their technical background.

20141218Recognising the value of topographic surveysContentFigDv2Driving efficiencies

Coffey recently adopted this approach on a site intended for large scale residential development. The site had 15m of uncontrolled and unrecorded fill, presenting challenges in predicting ground settlement for the engineering design team.

Coffey undertook onsite monitoring to assess the ground response to dynamic compaction. This included the use of topographic survey to map the ground surface deformation profile of the site. 

The survey data was used to help develop spatial plots of the print to heave volume ratio, to provide an indication of the consistency of the ground response to dynamic compaction.

As a result, we were able to see where soil was relatively dense (or stiff) and areas where it was relatively loose (or soft).

Geotechnical investigations were subsequently undertaken to confirm the results assessed using topographic survey.

This approach helped identify where significant compaction was needed – and importantly, where it wasn’t – delivering significant cost and time savings to the project.

How we can help

Topographic survey is a powerful tool to assist in quantifying the effects of various ground improvement methods.  It can deliver valuable insights on a complex site.

When not performed or done poorly, the results can be contradictory or confusing, which often leads to additional costs and or program delays. Coffey’s experience in using topographic survey to support geotechnical investigations means we understand how to effectively implement these programs to deliver successful outcomes.

If you would like to discuss how a good topographic survey can give you better results on your project, please contact Richard Moyle on +61 8 9269 6200 or via richard.moyle@coffey.com

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