Behavior of the Penetration Process of Model Jacked Pile in Layered Soil   Yu-nong, Li Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai, China e-mail: liyunong.nong@hotmail.com Jing-pei, Li Department of Geotechnical Engineering, Tongji University, Shanghai, China e-mail: lijp2773@mail.tongji.edu.cn
			ABSTRACT

This paper describes results from a series of experiments that has investigated the penetration mechanism of jacked piles in layered soils. A number of jacked piles were installed in a test chamber filled with saturated clay. Closed-ended piles with 50-mm diameters were used. The experiments were carried out to study how penetration resistance, dynamic end resistance and dynamic shaft resistance changed as the pile penetration depth was varied. We determined how the resistance and soil pressure changed as different soil interfaces were crossed during the pile pressing process. The results indicated that the shaft resistance decreases with penetration depth, a process known as ‘friction fatigue’. Moreover, the experiments were designed to investigate the effect of compaction of the jacked pile during sinking. The results revealed the soil displacement behavior produced by different positioning and the depth of the pile. We found that a lag effect existed between the maximum displacement and the pressed pile depth. The experimental results allow for a better understanding of the mechanical behavior and the inherent mechanism of compaction of the jacked pile during the penetration process. These results are important for estimating the influence of pile installation and guiding pile design during construction projects.

Keywords: saturated clay, jacked pile, penetration process, model test, end resistance, shaft resistance, compaction effect

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