C_±/C_c concept applied to compression of peat

Eight long-term multiple-stage-loading oedometer tests were performed on a fibrous peat from Middleton, Wisconsin. Both conventional-size and large specimens were treated with pore-pressure measurement. Load-increment duration and load-increment ratio were additional variables of the testing program. Time-settlement curves show that the coefficient of secondary compression (Cα) is not constant but increases in time under constant effective stress. Plots of Cαversus compression index (Cc) indicate that, for this peat, a poor linear relationship exists between Cα and Cc, and this relationship worsens if tertiary compression points are included. Plots of C_α/C_cversus void ratio show significant scatter but indicate that, in general, the C_α/C_cratio increases with decreasing void ratio. Load-increment ratio and sample disturbance are significant factors affecting the Cα versus Cc relationship. The fact that inorganic soils do not exhibit exaggerated creep effects or tertiary compression may explain, in part, the success of the C_α/C_cconcept for clays.