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Training critical to avoid unexpected ground conditions

Training to broaden geological experience and build confidence in generation of ground models is critical to avoiding unexpected ground conditions, according to GCG senior partner Jackie Skipper.

Skipper made the remarks during delivery of the 18th Glossop Lecture on the subject of “Variability and Ground Hazard: how does the ground get to be unexpected?” at the Royal Institution last night.

She also called on contractors to feed back more detail about the actual ground conditions found during construction to help build geological knowledge.

Skipper used her experience of working on projects in London and the London Clay and Lambeth Beds to demonstrate how depositional, tectonic, quaternary and Anthropocene change result in variable ground conditions.

She said that projects such as Crossrail were helping to build knowledge of the geology in London. “The ground is more variable than we thought even 20 years ago,” she said. “Changes made by man in the Anthropocene have made the ground even more complicated with significant underground assets.”

According to Skipper, ground hazards occur when the ground conditions vary from what is expected, whether the ground is better or worse than anticipated.

“A lot of ground investigations are not representative,” she said. “At 100% recovery you are just seeing 0.008% of the ground and, if you use borehole spacings recommended in Eurocode 7, you are seeing just 0.003%.”

Skipper said that this small insight is compounded by awarding work to the lowest ground investigation tender, negligible desk studies and poor logging and testing.

“Not understanding the ground conditions has a huge cost,” she said.

Skipper believes that greater investment in training and back analysis of actual ground conditions is a critical part of ensuring continuous improvement in ground engineering and avoiding unexpected ground conditions.

“We are in the Anthropocene era but we are also in the era of Instagram – we need to share hi-res images to help broaden knowledge and use these images to infer stratigraphy and faulting more,” she said. “We should be building a national archive of such images – maybe the British Geological Survey should become a repository for an image library?

“Essentially, we need to stop perpetuating the myth that understanding the ground is a waste of money. Good observation and interpretation are an investment.”

 

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