Experimental investigation on dynamic compaction for reinforcement of liquefiable sandy silt foundation

In light of the significant presence of liquefiable sandy silt layers in the foundation of the airfield area at the Beijing Daxing airport, this study employed a low-energy, small spacing, and low blow count dynamic compaction method to treat it.To assess the compaction effects and determin the parameters of the compaction process, two energy levels of 1 000 kN·m and 2 000 kN·m were selected, with each energy level tested at 4, 6, 8, 10, and 12 blow counts. Additionally, the effect of the surface frozen soil layer on compaction was investigated using 1 000 kN·m energy level with 4, 6, and 8 blow counts. The full depth standard penetration, surface wave and dry density tests were carried out in the dynamic compaction test area. The experimental results revealed that the sandy silt soil foundation exhibited increased compaction, propagation wave velocity, and enhanced liquefaction resistance after dynamic compaction. Optimal blow counts were determined as 10 and 8 for energy levels of 1 000 kN·m and 2 000 kN·m, the corresponding dynamic consolidation depth is 4.5m and 5.5m, and the eliminating liquefaction depth is 4.3m and 5.3m, respectively. Besides, the standard penetration test requires a minimum of 10 and 12 blows in the depth range of 4.5 m and 5.5 m for energy levels of 1 000 kN·m and 2 000 kN·m. At the optimal blow counts, the dry density of the surface layer of the original foundation should not be less than 1.45 g/cm³. The experimental results suggest that, for foundation treatment in the runway area, the dynamic compaction level of 2 000 kN·m is suitable, and 1 000 kN·m dynamic compaction level is used for foundation treatment in the apron and taxiway area.