Mahmoud Ghazavi - Associate Professor, Department of Civil Engineering, K.N. Toosi University of Technology, Tehran

This paper describes a new one-dimensional finite element model for pile driving in soft rock. The approach of Smith (1960) is used to simulate the pile driver system. The pile is assumed to be elastic, linear, and vertical. It is also discretised into a number of simple elements connected at nodes. The soft rock resistance acting at the pile nodes is calculated by spring and dashpots and the shear resistance of the rock is calculated using the Mohr-Coulomb failure criterion. The resistance of the soft rock incorporates a non-linear exponential function to account for rate effects resulting from pile driving. The computed values of pore pressures generated along the shaft, resulting from shear stresses and changes in total stress are compared with laboratory data obtained from an instrumented pile shaft driven in a saturated soft rock. These comparisons show that the model predicts the set and stresses associated by pile driving well.

Piled foundations, pile driving, pore pressures, Mohr Coulomb criterion, soft rock rate effects