Penetration of driven piles into pre-crushed blasted rock : Case Jätkäsaari

This paper deals with the ability of three driven pile types to penetrate a 0/300 mm pre-crushed blasted rock used as a fill material in the area of Jätkäsaari, Helsinki. The aim of this study was to test whether driven piles can be used as a foundation method in this fill instead of the more expensive drilled piles. In order to achieve that, a test area was created in Ahdinallas, Jätkäsaari. Piles with similar capacities of 300×300 reinforced concrete, RR170/12,5 steel pipe and TRM170/13 ductile iron were driven. The ground conditions in the test-piling area comprised of a 25-30 meter pre-crushed blasted rock layer, underneath of which was a 2-5 meter moraine layer. Thirty-three piles were driven in total, all equipped with a rock shoe. The area was laser-scanned prior and after piling. A pile driving record was kept, and inclinometer, torch, and PDA/CAPWAP measurements were made on the piles. All the piles that penetrated only the pre-crushed blasted rock stayed intact and were successful. Steel pipe and ductile iron piles however, penetrated the material with more ease and less hits/meter. As long as a pile would surely penetrate only a pre-crushed blasted rock layer, all of the tested pile types would be suitable for use as a foundation method. If there is a chance, however, that larger rock pieces are present, steel pipe piles or ductile iron piles would be a safer choice.