Properties of soils improved by different cement deep mixing methods

Representative methods for deep mixing in cement stabilisation treatment of grounds include mechanical mixing, jet grouting, and trencher mixing. These methods differ not only in their stabilisation mechanisms but have also evolved independently, and are seldom employed simultaneously at the same site. Consequently, despite forming similar cement-treated soils, their quality has not been compared directly. A unique opportunity arose to construct a quay wall using these three deep mixing methods, enabling the sampling of cement-treated soils from the same site. These were analysed through various mechanical tests, elemental mapping by micro X-ray fluorescence, and scanning electron microscope observations. Specifically, comparisons were made regarding strength, deformation modulus, failure strain, calcium content, and formation of hydration products. The results revealed that, across all ground improvement methods, the field strength was comparable to or greater than the laboratory strength, and the cement-treated soils displayed typical characteristics of such materials. Nevertheless, it was observed that the cement-treated soils formed by jet grouting and trencher mixing exhibited a tendency towards greater heterogeneity.