MU Farid, MSc, BSc(Eng) Hons. Lond, CEng, MIMechE, FIMarE. This paper was first published in GE’s May 1979 edition.
As part of its continuing research on steel bearing piles, an investigation was carried out by British Steel Corporation in an attempt to gather data which would illuminate those areas of contention involved in the raising of limiting stress levels, so as to allow economies to be made and customers’ confidence to be increased in the selection of steel bearing piles for a particular application.
To assess the characteristics of dynamic and static loading a strain gauge measurement technique was used. Blow-by-blow stress analyses were carried out. In total 700 blows were examined. The full record of the 700 blows and static observations can be obtained from the Welding Research Department, of BSC’s Teesside Laboratories, Middlesbrough.
The results reveal that during the course of driving a pile through hard strata, the impact stresses were 0.6 to 0.7 times the minimum yield stress, at the last blow. These impulsive stresses had no discernable effect on the structure of the piles. Results obtained suggest that considerable increase in design stresses might safely be adopted for steel bearing piles. One of the aims of this long-term research is to produce a dynamic testing system which gives more accurate results than can be obtained from traditional methods.