| Abstract | In this study, a total of 33 CIU triaxial tests have been conducted to investigate the
undrained strength behavior of the base clay and cement treated Bangkok soft clay at higher
water content. The remolding water content (w*) varies from 100%, 130%, to 160%, and the
water content to cement content ratio (cw/Aw) ranged from 5 to 20. The cement content (Aw),
vary from 5% to 22%. The results demonstrated that cement treatment modify the soft
Bangkok clay from normally consolidated to overconsolidated state. The degree of
overconsolidation is influenced by the cement content, the preconsolidation pressures and the
water content. Generally, the higher cement content, the lower preconsolidation pressure and
the lower water content (near the LL); the higher the degree of overconsolidation and the more
brittle behavior. On the other hand, the lower cement content, the higher preconsolidation
pressure and the higher water content (more than LL); the lower the degree of
overconsolidation and more ductile behavior. At higher cement content (Aw2::10%), the
preconsoliadtion pressures from 50 to 200kPa have no effect on the stress-strain characteristic
of cement treated clay because the mean yield stress is much more higher than the
preconsolidation pressures. At the same cw/ Aw ratio, the strength of the treated soil is not the
same. Moreover, the water content has bigger effect than cement content on the undrained
strength of cement treated clay, especially for cement content equal to or greater than 10%.
For any ratio cw/Aw such that the cement content, Aw2::10%, the strength behavior is
governed by the mixing water content; the closer the mixing water content to liquid limit, the
higher the strength developed for certain ratio cw/Aw. For any ratio cw/Aw, such that the
cement content Aw<10%, the strength behavior is governed by the cement content; and the
higher the Aw, the higher the strength developed for certain value of cw/Aw. Furthermore,
there is an optimum clay water content, which is found close to the Liquid Limit of the base
clay, that the treated soft Bangkok clay can get the highest strength at particular cement
content. For remolding water content varying from 100%, 130% and 160%, the corresponding
minimum optimum cement content are 10%, 15% and 20%, respectively, for cement treated
clay. The failure criterion of samples with cement content of Aw2:: 10% is bulging failure and
eventually the samples split associated with shear failure. In contrast, the failure criterion of
the samples with cement content of Aw<10% is the shear failure with distinct failure plane.
Finally, an empirical strength development equation is proposed for the Bangkok treated clay
with cement content (Aw2::10%). |
