Experimental and Numerical Analysis of the performance of pile group subjected to downdrag force before loading

Document Type : Review Article

Authors

1 Geological and Geophysical Engineering Dept. Faculty of Petroleum and Mining Engineering, Suez University, Suez-Egypt

2 Geotechnical Engineer Dept. Faculty of Engineering, Tanta University. Egypt

3 Civil Engineering Dept. Faculty of Engineering, 6th October University, Egypt

Abstract

Negative skin friction is the most common problem in the design and construction ofpile foundations in soft ground when the soil next to piles moves down more than thepile. Three main reasons cause negative skin friction, first is increase of verticalstress, second is development of additional compressive force, third is excessive ofpile settlement, these problems cause difficulty in construction and maintanance.Failure of the pile foundation from the servicability point of view might occur due tonegative skin friction. It has been concluded that less dragload occurs in piles in agroup due to pile-soil-pile interaction. In this research an exprimntal model for pilegroup installed in soft clay bed is carried out. The effect of downdrag force on pilegroup has studied with the varaible of piles spacing ratio, S/D, and the drainage stateof the clay stratum. Weather single or double drainage are also investigated atdifferent piles groups. Finally a comparison between single pile and pile group withthe same case of loading is studied to shed some light on the group effect.The resultswere numerically validated and verfied to study the obtained load values at diifrentcase. There is a good agreent between exprimental and numerical results. Also the thenumerical anaysis is helpd in better understand the induced drage loads and piledeformation. It also demnstrated that, the higher cohesion has a higher dragload. Forcase of Cu =30kPa, the dragload for pile group of spacing S =4D, 3D are 1.22, 1.05time of single pile.

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