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Interlink between Metastability Index, MI(G)
and Undrained Shear Strength in Aged Holocene Clay Deposit
Minoru Temma, Satoru Shibuya, Toshiyuki Mitachi and
Nobutaka Yamamoto
ABSTRACT : The term "ageing
effects" means alternations of mechanical properties of clay after
sedimentation. In this paper, it is considered that ageing effects
involve with metastabilization of clay structure, which in turn results
in increase of elastic shear modulus, G at a given density. In an
attempt to examine the interlink between Metastability Index, MI(G)
and normalized undrained shear strength, a series of triaxial
compression tests was performed on a total of six marine clays
worldwide. As a result, a method for distinguishing the effects of
cementation and secondary compression is proposed. In addition, similar
case studies were carried out at two sites in Ariake (Japan) and in
Bangkok (Thailand). Applicability of MILK (Metastability Index
coupled with Laboratory K0-test) method for estimating
cu "in the ground" (Shibuya et al., 2000)
was also examined with the results of triaxial compression test on
natural as well as reconstituted samples. The degree of ageing at
different depths was evaluated in each site by having the profile of
Metastability Index with depth. The ca-profile with depth in aged
natural sedimentary clay ground is discussed in link with the
site-specific MI(G) -profile with depth.Key words: aged
effect, clay, sample disturbance, shear strength, triaxial compression
test (IGC: C3/D3/D5/D6)
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