A new formula to estimate the strength of cement-treated clay was proposed by the authors instead of the conventional formula determined by water-cement ratio. The key parameter in the new formula is a volumetric solid ratio, which is defined as a volume ratio of soil plus cement to the total volume of cement-treated soil. However, it is not clear how to consider the effect of sand or gravel contents on calculation of the solid volume ratio to use the new formula. A series of strength tests of cement-treated clays were carried out with various sand contents, initial water contents and cement contents to study the applicability of the new formula. It was found that the two parameters; cement content and volumetric solid content used in the strength estimation formula should be defined to the mass and volume of clay and silt of soil, neglecting the sand content. Based on this finding, a modified formula is proposed. The strength estimation using the modified formula showed the best fitness between the measured strengths and the calculated strengths, compared to the water-cement ratio equation and the volumetric solid ratio formula without modification. The modified formula can explain the strength development of cement treated soils with different initial water contents and the different sand contents by the same parameters.
In the coastal area, sediment dredging is regularly carried out to maintain navigable channel and harbor. Particularly for ports located in Seto Inland sea shown in Fig. 1, such as Hiroshima Port, Ube Port, Tokuyama Port, Fukuyama Port and Mizushima Port, dredging is necessary since the Seto Inland sea has a shallow sea depth and significantly affected by the ebb-tide. Generally, the dredged soil will be transported to a disposal facility installed in the harbor, but nowadays, most ports are running out of capacity due to the huge amount of the dredged soil generated every year, and constructing a new disposal facility is not feasible. Meanwhile, the disposal and recycling of dredged soil is a major task in constructing a new repository, for example, Ueno et al., (2012) reported the utilization of Tokyama Port dredged soil to construct a 293,000 m2 artificial tidal land.
