Different foundation soils will show three kinds of reinforcement characteristics under dynamic compaction effect: first, densification effect, which is characterized by gas discharge in soil; second, consolidation effect, which is characterized by pore water discharge; third, pre deformation effect, characterized by rearrangement of various particle components in structure and change of particle structure and shape. From the microscopic point of view, the strength growth of soft soil under dynamic compaction can be divided into the following stages:
1. Dynamic compaction loading stage. In the time of tamping, the energy energy generated by tamping is the dynamic stress of the foundation, which can make the water and gas in the pores be compressed gradually. When the percentage of gas is close to zero, it becomes that there is no tightening. At this time, the water pressure in the pores rises to be equal to the covering pressure.
2. Unloading phase. When the kinetic energy of tamping is removed, the dynamic total stress disappears, but the pore water pressure is still at a relatively high level. At this time, the pore water pressure is greater than the useful stress, so there is a large negative useful stress in the soil, and the soil will liquefy, resulting in cracks in the soil, the permeability of the soil is added, and the pore water is discharged.
3. Consolidation stage. Due to the disappearance of pore water pressure, the cracks in the soil will be closed, and the touch of soil particles will be tighter than that before dynamic compaction. The shear strength and deformation modulus of the diagram shall be added.
4. Soil thixotropic rehabilitation stage. After the pore water pressure disappears, the shear strength and deformation modulus of the soil will slowly increase, gradually reaching the intention of reinforcement.