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Behavior of Gravely Sand Using Critical State Concepts

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A series of consolidated undrain ed tria xial tests were performed in order t o understa nd t he behavior of a grave ly sand. Th e mat erial was selected from Tehran alluvium and is classif ied as gravely sand in t he Unified Soil Classificati on System. Criti cal state concept s were used for interpretation of t he behavior of t he soil. T he criti cal state line in q - pי space was reasonably unique. However, it was not possible to define a uniqu e crit ical sta te line in e-In pי space. Th e overall scatter, in t he cr it ical st ate line for the gravely sand studi ed, was ± 0.04, in terms of void ratio. Two reasons can be ident ifi ed for thi s scatte r. The first reason is t he inevi table error in void ratio calc ulat ion and th e second is that th e behavior of thi s mat erial, even at a crit ical sta te, is fabric and stru ct ure dependant . On th e basis of th ese tests, it has been concluded t hat, for t his material, a crit ical state zone with upper and lower limits can be defined. Neverth eless, a unique boundary surface can be defin ed by present ing th e data in norm alized stress space.

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