Abstract: Dynamic loading tests and mesoscopic tests were carried out to study the correlation of strength indices and mesostructure parameters, which commonly degrades for disturbed structural clay. It is found that cyclic torsional and simple shears cause a remarkable strength degradation for structural clay, in the range from 20% to 50%. The strength of silty clay after external disturbance is still greater than that of the reconstituted silty clay. Cohesion and friction angle of the disturbed silty clay degrade dramatically and then decrease to a stable value with the increasing of disturbance times. The investigation of five typical mesostructure parameters show that the growth rate of void for transverse sections subjected to the torsional shears is similar to the longitudinal profile. However, the void growth of longitudinal profile is greater than the transverse value subjected to simple shears. There is a linear attenuation between post-disturbance cohesion ratios and void number at the early period, and then the cohesion will become a constant value. By contrast, there is no convergence between friction angle ratios and void number ratios.

Key words: saturated clay, strength attenuation, microstructure parameter, void number