Abstract: The testing results of dynamic compaction on a silty soil foundation of a flood-prevention dam in Yibin, Sichuan Province are introduced. The test data show that: the valid strengthened depth in the foundation is more than 6 meters at the compacting energy of 1 600 kN?m; the average dry density of the soils is increased from 1.48 g/cm3 to 1.57 g/cm3; the average void ratio is decreased from 0.852 at natural state to 0.724 after compaction; the average compression modulus is changed from 5.42 MPa to 8.27 MPa; the average permeability coefficient is decreased to the value of less than one-tenth of the natural state; the arithmetic average of permeability coefficients is reduced from 2.5×10-4cm/s to 3.5×10-6 cm/s; the N-values of SPT at natural state have 32.9 % less than 5 while all of them are more than 7 after compaction. The conclusion can be stated that the dynamic compaction method is suitable for the treatment of the silty soil foundation in the site of the foundation of flood control dam in Yibin. The ground can meet the requirement as the foundation of flood-prevention dam on capacity and seepage stability, as well as the liquefaction prevention at 7-degree earthquake.

Key words: dynamic compaction, field and laboratory test, bearing capacity, seepage stability, liquefaction