It has always been a difficult problem to determine the safe interval of vibration influence during dynamic compaction machine construction, which involves the determination of Safety specifications, the characteristics of foundation soil, the size of dynamic compaction function level, the size of rammer area and so on. It is difficult to give proper data without field vibration inspection, but not every project has the conditions to do it, especially in the preliminary stage of foundation treatment plan.
The vibration produced by dynamic compaction machine construction has the following laws:
1) The main frequency of dynamic compaction machine vibration is generally below 50 Hz and decreases with the increase of interval.
2) In a short interval, the vibration wave of dynamic compaction machine is loose to the surrounding mainly by surface wave. The vibration intensity decreases with the increase of the distance from the vibration source. The attenuation rate of vibration intensity is related to the characteristics of foundation soil. When the local foundation soil layer is weak, loose, low density, and thick, the vibration intensity decreases actively; when the local foundation soil layer is stable and dense or the soil layer is weak and thin, and the underlying soil layer is stable, the vibration intensity decreases slowly.
Lease of dynamic rammer
3) When the vibration source point of dynamic compaction machine is located at the low relative elevation, the vibration effect at the higher relative elevation is expansion; when the vibration source point of dynamic compaction machine is located at the higher relative elevation, the vibration effect at the lower relative elevation is attenuation.
4) The vibration intensity increases with the increase of energy level and decreases with the decrease of hammer area.
Dynamic compaction machine is mainly used in construction, and for the construction of dynamic compaction machine, due to the need of soil compactor, there are many types of compaction machinery, one frog, vibration type, step-by-step, tamping, hanging hammer type. According to the needs of the project, different types of dynamic tamping machines are used to fix the foundation.
On the other hand, for the application of dynamic compaction machine, the main reason is that the height of some high impact hammers can be gravel, gravel, slag, which has good performance on the foundation strength, the formation of granular pier in the foundation, the formation of pier pier composite foundation, so as to improve the foundation bearing capacity and reduce settlement. In the process of dynamic replacement, the soil structure is destroyed, and the foundation soil produces excess pore water pressure, but the strength of soil structure will recover with time. Granular bridge piers generally have good water permeability, which is conducive to dissipation and consolidation of excess pore water pressure.