Experimental Study to Evaluate the Effect of Consolidation Behavior on Pile Setup

Abstract

Abstract This paper presents the field experimental results of static load tests (SLTs) and dynamic load tests (DLTs) that were conducted on instrumented prestressed concrete (PSC) test piles to characterize the pile setup phenomenon for individual soil layers along the piles' length. For this purpose, three PSC piles were driven at a bridge construction site in Lake Charles, LA, that were tested at different times after installation. The piles were instrumented with sister bar strain gauges to measure the load transfer along the piles' length, and pressure cells and piezometers to measure the total stress, effective stress and excess pore water pressure (PWP) with time and hence the setup for different soil layers along the piles' length. Multilevel piezometers were installed in the surrounding soil to evaluate the spatial distribution of excess PWP and to measure the influenced zone caused by pile driving. The load tests showed that the side resistance increased by 129 %, 99 %, and 91 % for the three test piles during the last load test. The case pile wave analysis program (CAPWAP) analysis of the DLTs and the load distribution plots from SLTs were used to compute the resistance of individual soil layers along the piles with time. The results showed that the soil layers with low undrained shear strength and high value of generated excess PWP exhibited higher amount of setup; while soil layers with low permeability and low coefficient of consolidation exhibited higher rate of setup compared to other soil layers. The results also showed that setup increased at a higher rate before the dissipation of excess PWP and the rate became much slower after the end of dissipation process. The dissipation of excess PWP (or consolidation data) was used to quantify the setup by its contributing factors (i.e., consolidation and aging effect). The results showed that a majority of setups was because of the consolidation effect. The results of multilevel piezometers indicated that the influenced zone because of pile driving was almost 3B (B = pile width) radial distance from pile face.