Effect of Soil Set Up on Pile Driveability in Chalk

This paper deals with the analysis of delay data and the effect of delay on pile driving resistance. Based on the analysis of observed pile driving data, the increase in soil resistance during driving is quantified in terms of Relative Set Up, F_R, defined as the ratio of soil resistance after delay to soil resistance before delay. The relative set up is found to increase with delay time and a correlation is developed between F_R and delay time. An extrapolation of the increased resistance during driving is used to estimate static capacity of piles. A comparison of this estimated static capacity and the computed static capacity shows good agreement. It is concluded that the soil resistance during driving may increase by as much as 80% if significant delays occur. It is believed that the values of F_R developed for this study can be used for planning pile installation procedures as well as for estimating static pile capacities in similar soils.