Discussion of 'Examining Setup Mechanisms of Driven Piles in Sand Using Laboratory Model Pile Tests' by Z. Zhang and Y. H. Wang

摘要

The authors conducted a pressurized chamber test, which was equipped with an advanced bender element system and tactile pressure sensors to examine the mechanisms of pile setup in sand. The findings of the paper are of significant interest and the discussers would like complement these findings with those from other experiments on this subject. The authors conclude that, in line with Axelsson (2000), the changes of stationary radial and hoop stresses in close proximity to the pile shaft during setup are minor and the soil stiffness and its corresponding rate of growth following pile installation are significantly higher. The same conclusion was drawn by Lim and Lehane (2015) from field experiments on instrumented jacked piles, which recorded a very small variation of stationary radial stress (σ′_(rs)) over a period of 72 days after installation. A comparison of the measured variations of shear stress with radial effective stress during the last installation pushes and during subsequent load testing indicated a significant time dependence of the radial effective stress change during shearing (Δσ′_(rd)).