Abstract: Based on a series of laboratory tests on soft soil in Nansha, Guangzhou, involving direct shear test, unconfined compression test, consolidation test, the structural characteristics of the regional soft soil are studied. By using undisturbed and remoulded soil samples, shear deformation, shear strength and consolidation properties of the structured clay which indicate the significant structure of the soil and the effect on engineering property are analysed. The test results show that the shear strength of disturbed structure clays obviously declines and the compressibility increases; the consolidation process of undisturbed samples can be considered as three phases, which relating to structure yield stress. For remoulded structured samples, the dividing line of compression and secondary compression by compression-log time curve, obtained from oedometer tests, is more obvious than undisturbed specimen, in case of loaded be same. It can be concluded that structure yield stress, which can be defined by compression coefficient a-consolidation pressure p curve, is one of the important factors for controlling deformation of structured clay. The influence of structure on mechanical properties decreases as the consolidation pressure increases. When consolidation pressure is higher than full structural yield stress, the effect of structure can be neglected.

Key words: structured clay, consolidation test, yield stress