Model test on pier formation effect of dynamic replacement in coastal soft soil

The depth and diameter of gravel pier replaced by dynamic replacement are important indicators to characterize the pier shape. While compaction parameter and construction method are important factors to affect the pier shape. It's very important to study the mechanism of dynamic replacement for optimizing the dynamic replacement process. A laboratory model test was designed based on the similarity ratio(δ=0.05) between model and prototype to study the influence of three independent factors including different ramming energies (0.018, 0.027, 0.036, 0.045 kN•m), different packng methods(1/4 packing, 1/3 packing, 1/2 packing, full packing), different hammer cone angles(0°, 30°, 60°, 70°, 80°) and their combined changes on the pier shape through remolding the model foundation formed by soft soil. The results show that the variation curve of pier diameter with replacement depth takes the maximum buried depth of pier diameter as the dividing point. The upper part satisfies quadratic polynomial distribution law, and the lower part satisfies linear decreasing law. The replacement depth is generally positively correlated with the ramming energy, and negatively correlated with the hammer cone angle. The hammer cone angle and the ramming energy have little effect on the diameter of pier, but the method of packing has a significant effect on the pier diameter and has a positive correlation with the expansion coefficient of pier. © 2021, Editorial Office of Journal of Building Structures. All right reserved.