ON THE STRESS-STRAIN BEHAVIOUR OF LIGHTLY CEMENTED CLAY BASED ON AN EXTENDED CRITICAL STATE CONCEPT

KIYONOBU KASAMA, HIDETOSHI OCHIAI and NORIYUKI YASUFUKU

ABSTRACT: In order to evaluate the effects of increasing cementation on the mechanical properties of lightly cemented soils, artificially cemented clay was prepared and a series of standard consolidation tests, undrained triaxial compression tests and constant mean effective stress tests was performed. Based on the experimental considerations, the effects of light cementation on the stress-strain behaviour and strength property are discussed. In addition, based on the theoretical considerations within the framework of the critical state concept, several basic concepts for the development of a constitutive model for lightly cemented clays are presented. The special characteristic of the presented model is the introduction of an internal variable which controls the effects of cementation. The following conclusions are obtained: 1) The failure state of lightly cemented clay may be determined in the balance of cementation, void ratio and stress condition. 2) The failure state line in the p - q space is parallel to that of an uncemented clay and has a certain intercept p_r, which characterizes the cementation effect. The slope of the failure state line in the e - 1n (p+p_r) space becomes steeper with any increase in cementation effect. 3) A constitutive model incorporating cementation is proposed. Introduction of a soil constant p_r is effective in estimating the mechanical properties of lightly cemented clay.

Key words: Cam-Clay, cement, cementation, cement stabilization, clay, constitutive equation of soil, shear strength, triaxial compression test (IGC: D6/D1O)