عبدالرضا فاضلی

In general, conducting 32 experiments involving real-scale field, medium-scale field and medium-scale laboratory tests, this study evaluates the penetration rate of 6 close-end, cone-shaped cylindrical hollow steel piles with the end angles of 37, 44, 53, 67, 90 and 127 degrees under the compaction caused by the high-frequency hammer blows. The pilot tests were conducted in the sandy soils of Niayesh region in the Bushehr port and the new city of Alishahr, and the results were evaluated. Although, according to the results, the penetration rate of the piles is increased by decreasing the tip angle of the end cone (more sharpened cone) due to the increased stress in the compaction area, however, the large reduction in the tip angle of the end cone leads to an increase in the length of the cone-shaped region and the decrease in the compacting action of the surrounding soil. On the other hand, the use of piles having larger tip angle of the end cone reduces the penetration rate and also causes the premature depreciation of equipment in this system. Accordingly, it was observed that although the use of a pile at the 37° tip angle of the end cone increases 22-24% the penetration rate relative to the pile with the 127° tip angle of the end cone, however, with a 5-fold increase in the length of the end cone, the total effective length of the pile will be reduced. The field experiences of pile (shuttle) driving in the gravel impact compaction piers systems in several case studies conducted in Bushehr province show that the cones with a 60° tip angle, providing adequate effective length for the pile as well as ease of driving of the pile into the soil, are an ideal cone for the sandy soils. According to the results of experiments at 60° in three different sandy soils, it was observed that the use of this pile comparing a pile with the 37° tip angle of the end cone increases 6-10% the energy required for the driving. Furthermore, the length of the cone with the 37° end-cone ti