Abstract：A fundamental understanding of the macro-meso mechanism of dynamic compaction of sandy soils using a modified visible model test apparatus，which is designed by authors，is carried out. A series of model tests of dynamic compaction are conducted on sandy soil with a new technique for real-time visualization and photographing；and soil displacement and dynamic stress are monitored for each case. The experimental results show that the technique can be used successfully to visualize the meso-scale change of sand grains fabric including orientation and average coordination apart from displacement. It is found that the optimum hitting number of each pass is about 8 for sandy soils；and the macro-mechanical results of dynamic compaction are the increase of ground displacement and decrease of void ratio；and the meso-scale mechanism is the process of grains rearrangement from disorder to orientation and increase of average coordination. The findings of this study will be beneficial to the innovation and determination of parameters for dynamic consolidation and the research of macro- meso response under impact loading.
