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Should HAE filters be used in the fully-grouted method?

Jul 23rd, 2018

Geosense piezometers have been used as part of a recent study into the use of HAE and LAE filters in the fully-grouted method carried out by researchers at Aarhus University in Denmark.

The results were presented by Thomas Simonsen and Kenny Sorensen in a paper at the International symposium on Field Measurements in GeoMechanics (FMGM) in Rio de Janeiro last week.

The paper, entitled The Performance of Vibrating Wire Piezometers in Very Low Permeable Clay, identifies that using HAE filters in the fully-grouted method can produce unexpected results compared with LAE.

Martin Clegg, Geosense Managing Director and a member of the ISO TC182/WG2 committee – an organisation currently developing international standards for 
geotechnical monitoring under ISO, said: “This subject is a hot topic and highlights the confusion within the industry. Basically, the question is should HAE filters be used in the fully-grouted method?”

The Aarhus research demonstrated the problems of using HAE filters, even using five different saturation methods. They concluded that it is ‘highly recommended that low entry LAE filters are chosen for use in the fully grouted-method’.

“We know from experience that sometimes the high entry option works in the fully-grouted method but more often, it produces erratic readings. The real problem is that nobody has been able to explain this and it is all too often put down to sensor failure. This is why we decided to support the research at Aarhus,” said Martin.

“There have been discussions between several leading experts in the field, including John Dunnicliff and Erik Mikkelsen, and it has been pointed out that the fully-grouted method was developed for use with LAE filters. There is a question mark over whether it should ever be used with HAE filters.”

If you are interested in this, please share your views and experiences.

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