Strength and stiffness of cement-treated marine dredged clay at various curing stages

This paper evaluates the unconfined compressive strength ([q.sub.u]) and stiffness ([G.sub.0]) of marine dredged clay treated by ordinary Portland cement. Although the cement-treated marine dredged clays have been used as filling materials for construction or reclamation, many of previous studies were more applicable to soft foundation improvement methods such as deep cement mixing and jet grouting. This study aims to investigate how the [q.sub.u] and [G.sub.0] of cement-treated marine dredged clay vary with water and cement contents at various curing times and to observe the relationship of the [q.sub.u] and [G.sub.0]. A series of unconfined compression and bender element tests were carried out for cement-treated Tokuyama dredged clay with different values of water and cement contents at various curing times, ranging from 5 h to 90 days and the relationship between the [q.sub.u] and [G.sub.0] was examined. Specific volume normalized by that at liquid limit were applied to facilitate parametric study. The study revealed that the behavior of [q.sub.u] with curing time are closely similar to that of [G.sub.0], and a trend of development of [q.sub.u] and [G.sub.0] change before and after 3 days of curing time. The [q.sub.u] and [G.sub.0] can be correlated with the normalized specific volume. The [q.sub.u] and [G.sub.0] exhibits a linear relationship for the curing time. Based on these results, the empirical equations for estimating [q.sub.u] are proposed using [G.sub.0] estimation equations and the relation between [q.sub.u] and [G.sub.0]. In addition, the applicability of formulas based on the relation of [q.sub.u] and [G.sub.0] was evaluated using the relation of [G.sub.0] and secant modulus ([E.sub.50]). It was confirmed that the [G.sub.0] can successfully describe the improvement effect of cement-treated marine dredged clay and can be used to effectively predict the [q.sub.u] using the proposed formulas. Keywords: Dredged marine clay Bender element test Unconfined compressive strength Stiffness Specific volume Secant modulus
1. Introduction Every year in Japan, large amounts of clayey sediment soil that are deposited on the bottom of the sea are dredged to maintain ports and waterways [21]. Since [...]