If it is a granular material/soil why not use a Nuclear Density Gauge, in
backscatter mode (i.e. surface measurement), depth of measurement is around
200mm I think. Thus you can measure each lift (NRSWA - max thickness of
layer is 200mm as i recall) and in between passes to monitor build up of
the density.
However, if you want to profile the density within the layer (i.e. at say
500mm intervals) then in direct transmission mode you can insert the NDG
probe to the required depth. This latter method does require a 'mandrel' to
be driven in to the backfill to then insert the probe into.
We have tried density profiling in 150mm of type 1 sub-base to monitor
density changes during compaction on differing stiffness substrate support
in recent fieldwork for a new specification for highway works at Loughborough.
hope this helps, best regards David
Paul
PS currently doing work on indirectly assessing 'quality' of compaction by
stiffness and also Clegg Hammer (good correlation of Clegg to density in
general but obvious concerns re depth if influence and particle size)
At 15:53 08/02/01 +0000, David Hughes wrote:
>Has anyone any ideas on how to measure the compaction of backfill in a
>trench? I would like to monitor density with depth during compaction.
>
>The measurement needs to be carried out in a non destructive way (ie no
>excavation after compaction)
>
>I'm thinking along the lines of pressure cells or strain coils.
>
>Any other ideas? Is the dynamic measurement of surface compaction reliable!
>
>thanks
>
>David
>
>
>---------------------------------------------------------------------
>Dr David Hughes CEng
>School of Civil Engineering
>Queen's University Belfast
>Belfast BT7 1NN
>N Ireland
>
>ph +44 (0)28 90 274014
>fax +44 (0)28 90 663754
>----------------------------------------------------------------------
>
>
Dr Paul R Fleming
Lecturer in Geotechnical Engineering
Dept. of Civil and Building Engineering
Loughborough University
Loughborough
Leics LE11 3TU
Tel: 01509 222616 (Direct)
Tel: 01509 222637 (Secretary)
Tel: 01509 222884 (Dept General Office)
Fax: 01509 223981 (Department)
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