Dear Hooshang,
During soaking of CBR samples the top surface is free to swell and soften
(unless you have used surcharge weights?) whereas the bottom surface is
constrained by the bottom plate, even if a perforated plate is used.
Therefore you would expect lower values of CBR from the top surface. This
should be consistent with higher water contents at the top.
You might expect some difference between top and bottom even in unsoaked
tests as the horizontal stresses that develop at the bottom of the mould are
likely to be higher.
However, 400% difference sounds very significant. Could it be due to the
grading of the calcareous soil changing under compaction? It might be worth
checking to see whether the breakdown is greatest at top or bottom by
checking the particle size distribution after compaction.
Regards
David Toll
*******************************************
Dr David Toll
Nanyang Technological University
School of Civil & Structural Engineering
Blk N1, #1A-37, Nanyang Avenue
Singapore 639798
Tel: +65-790 6429
Fax: +65-791 0676
e-mail: [log in to unmask]
WWW: http://www.ntu.edu.sg/home/cdtoll/
-----Original Message-----
From: Hooshang Katebi [mailto:[log in to unmask]]
Sent: 10 February, 2000 2:19 AM
To: [log in to unmask]
Subject: Tabriz Calcareous Soil
Hello Everyone.
I am conducting a thesis into the Engineering Behaviour of Calcareous soils,
and I am about to carry out some soaked CBR tests.
The primary tests showed that there is considerably difference between the
CBR of the top and bottom of soaked samples (more than 400%). I am in need
of literature on this subject to evaluate my testing program and to have a
better judgement of the interpretation of the results. Can anyone point me
to publications, which give information on the difference between the
strength of the top and bottom of samples?
I am also interested in hearing of any cases where the use of ground
improvement methods may have been implicated in Calcareous Soils.
I appreciate your response.
Regards
Hooshang Katebi
Tabriz University
E-mail: [log in to unmask]
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