Abstract: To explore the strength properties of undisturbed sample and remolded sample of Zhanjiang strong structured clay under different stress paths and its relevance to the soil structure, the stress path tests of such as conventional triaxial compression(CTC), reduced triaxial compression(RTC) and conventional triaxial extension(CTE) under different consolidation conditions are carried out, the mechanical behaviors as well as the strength properties of strong structured clay are analyzed. The results show that the shear failure modes of Zhanjiang clay mainly include unitary type, double crossover shear zone and waist drum type; and the stress-strain properties mainly include mild strain softening, intense strain softening, mild strain hardening and intense strain hardening. The failure strain of all the samples under anisotropic consolidation is less than that of isotropic consolidation while the breaking strength and initial elastic modulus are larger. The strength properties of clay under different stress paths are mainly reflected in the change of effective cohesion before the structure yielded; undisturbed sample has a higher cohesion and lower frictional angle compared with the remolded sample; but after structure yielded, the cohesion decreases and the frictional angle increases gradually. The transition from undisturbed sample to remolded sample is a growth and decline process of cohesion and friction inside the microstructure of clay. Based on the results, it is pointed out that the strength indexes of strong structured clay before the structure yielding has a quite strong dependence to the stress paths.

Key words: Zhanjiang clay, strong structure, stress paths, strength properties, cohesion, structure yield