A Study on Duplication Method of Undisturbed Natural Clays in Laboratory

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Relationships between physical properties, consolidation characteristics and shear characteristics and mixing conditions of artificial clays mixed a kaolin with a bentonite were investigated in order to develop the duplication method of undisturbed natural clays in laboratory by using marketed materials.As the results, it is found on physical properties that the liquid limit of mixed clays linearly increases with an increase of the bentonite content of the mixed clays and that the rate of its increase decreases with an increase of the salinity of the mixing water.On the other hand, the plastic limit is hardly influenced by the bentonite content of the mixed clays or the salinity of the mixing water.It is found on consolidation characteristics that the compression index of the mixed clays linearly increases and the logarithm of the coefficient of consolidation linearly decreases with an increase of the bentonite content of the mixed clays.It is also found on shear characteristics that the excess pore water pressure caused by shearing decreases, shear strength increases and the degree of the strain hardening increases with an increase of the bentonite content of the mixed clays.In order to duplicate the aging effect in laboratory, the mixed clays were reconsolidated at the high temperature from the slurry state or cured at high temperature only during the secondary compression of the last reconsolidation stage.As the results, it is found that the consolidation yield stress of the clay samples reconsolidated or cured at high temperature becomes large than that of the clay samples reconsolidated at room temperature and that the characteristics of the clay samples reconsolidated or cured at high temperature are similar to those of naturally aged clays.This implies that the high temperature reconsolidation procedure and the high temperature curing procedure can duplicate the aging effect.