Date of Award

2009

Degree Type

Dissertation

Department

Civil and Environmental Engineering

First Advisor

Khan, Lutful

Subject Headings

Piling (Civil engineering) -- Testing, Clay soils, Electrokinetics

Abstract

A significant increase in the load capacity over a period of time is often observed in driven piles. This time dependent strength gain is termed as 'set-up'. Different mechanisms have been proposed to explain the set-up phenomenon in cohesive soils. A research was initiated to investigate this mechanism in clay soils in terms of electrokinetic theory and explore the possibility of accelerating the process. The system chosen for the study consisted of laboratory scale steel piles driven in kaolinite clay under controlled conditions. The piles were subjected to DC voltage gradients with surrounding electrodes at different time intervals and their capacities were compared with those of the control piles. Tests were also conducted at varying moisture contents and various clay-sand mixtures. The capacity gains of piles in kaolinite clay under 1, 10 and 30 V D.C., compared to those without any external electric gradient, were 73 , 116 and 162 respectively. Higher clay content produced higher set-up. On the basis of laboratory tests, it was concluded that pile set-up in kaolinite clay could be significantly accelerated by electrokinetic method. An empirical equation incorporating the effect of an applied electric gradient was proposed to predict pile set-up in clay. The proposed equation was in good agreement with the experimental data

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