One-dimensional consolidation of lime-treated dredged harbour sediments: Fid-Bau Portal

One-dimensional consolidation of lime-treated dredged harbour sediments

Wang, Dongxing / Abriak, Nor Edine / Zentar, Rachid

Dunkirk marine sediments can be used as an alternative roadbed material, and a full-scale test road using this has been successfully built at Dunkirk harbour in France. In this context, the long-term deformation behaviour of Dunkirk sediments is of crucial importance in the evaluation of roadbed deformation. The standard oedometer tests were carried out to plot the e-logσ′ and e-logt curves, which were used to determine the compression index (C_c), swelling index (C_s) and coefficient of secondary compression C_α during loading and unloading. The effect of lime treatment on primary and secondary compression behaviour was investigated. The soil structure influences greatly the yield consolidation stress σ_y′, which is increased with lime content. Both σ_y′–e_y (void ratio at σ_y′) and C_c–C_s relations are analysed. It is observed that σ_y′ is connected with e_y by a power function and C_c/C_s varies between 0.013 and 0.1. C_α remains low at consolidation stress σ′ < σ_y′ and reaches a peak at σ′ = (1 – 4) σ_y′ followed by a decrease in C_α. Lime addition induces the peak C_α moving towards a larger consolidation stress of 5σ_y′. Based on the C_α–lg(t/t_p) curves, it is interesting to note that t = 20t_p (end-of-primary consolidation time) is suggested as a sufficient consolidation time to study the secondary compression behaviour of marine sediments. The C_α/C_c ratios of various clays including Dunkirk sediments show that C_α/C_c changes mainly in the range of 0.02–0.05. However, the C_α/C_c ratio is different for lime-treated sediments (C_α/C_c* = 0.0164) and untreated sediments (C_α/C_c* = 0.0432). Two separate zones in C_α–C_s* plot are clearly observed for untreated and treated sediments with boundary line of C_α = 0.0433C_s* – 0.0008.