Abstract: We carried out cyclic impact and consolidation tests with different intermediate  principal stresses on saturated fine sand by using improved SPAX-2000 true triaxial testing system, and investigated the mechanical responses of the sand such as stress-strain relations and strength variation of specimen after the impact loading under different conditions. Results showed that: when intermediate principal stress increased, the specimen under impact loading was easily tend to be dense, and shear strength was largely improved; when the frequency of impact load was lower and the intermediate principal stress smaller, shear strength of the specimen increased significantly, while when the second principal stress was larger, shear strength of the specimen rarely varied. The results indicate that intermediate principal stress and frequency of impact load are important factors affecting the dynamic consolidation.

Key words: true triaxial test, cyclic impact load, intermediate principal stress, fine sand, law of mechanical response