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Model pile raft system was pushed in the consolidated clay bed until the raft touched the organic clay top. It was ensured that while performing tests on piled raft and individual raft, there was a full contact between the soil layer and the raft. The settlement was measured using two dial gauges having a 50 mm range with 0.01 mm sensitivity. They were placed diagonally opposite on the model raft to get average settlement at the center of raft. Loads were applied in gradual increment and settlements were recorded till there was no appreciable change in settlement for a particular load increment. Then the next load increment was applied. The tests were continued until the settlement was more than 10% of width of corresponding raft.
V. Results And Discussions The Figs. 5 to 10 shows the load settlement curves with different number of piles and also the comparasion between different thicknesses for 100 and 200 mm width flexible and rigid piled rafts with 1, 4 and 9 piles respectively. It is observed from these figures that the load carrying capacity of the piles increase as the size of the raft increase. The load vs. settlement curve for free standing piles with different area ratio (Rarea).
Area ratio (Rarea) is defined as ratio of area of piles to area of raft expressed as percentage. It is observed that the piles with low area ratio settles faster than the with high area ratio. From the results of this study, the following conclusions can be drawn. It was obtained that the settlement in the pile group standing alone are fast in settling in the beginning and reduced after some loading, but in case of raft alone slow settlement is observed.
The piles take a major portion of total load at the initial stage of loading, but after yielding, a considerable portion of total load is transferred by the raft. The settlement reduction ratio (immediate) of a piled raft decreases with increase in pile to raft area ratio as well as pile slenderness ratio. When the pile to raft area ratio decreases the settlement reduces, i.e. in the thesis pile to raft area ratio ranging from 28.26, 12.56, 7.07, 3.14 and 0.79, the settlement reducing is decreasing from 28.26 p-r ratio to 0.79 p-r ratio.
DOI: 10.9790/1684-1304078388 www.iosrjournals.org 86 | Page Effect Of Number Of Pile In Pile-Raft System In Organic Clay
From the results of this study, the following conclusions can be drawn:
It has been observed that piled raft foundation concept has significant advantages in comparison to conventional foundation for some soft clay. The ultimate bearing capacity of Piles will be increased and the settlement of Pile is reduced as the diameter of Pile increases. It is obtained that the settlement in the pile group standing alone are fast in settling in the beginning and reduced after some loading, but in case of raft alone slow settlement is observed. The piles take a major portion of total load at the initial stage of loading, but after yielding, a considerable portion of total load is transferred by the raft. The settlement of raft depends on raft thickness; increasing the thickness of the raft the settlement reduction can be noticed. The settlement reduction ratio (immediate) of a piled raft decreases with increase in pile to raft area ratio as well as pile slenderness ratio.
This analysis may be useful in design of piled raft in soft consolidating, organic, clayey soil. The settlement reduces when the slenderness ratio s/d reduces. The increases in number of piles in a piled raft foundation results in increase in ultimate bearing capacity and decrease in settlement.
ReferencesCooke, R.W. (1986). “Piled raft foundations on stiff clays: a contribution to design philosophy”. Géotechnique, 36, No 2, 169-203  Thakare.S.W, and Pankaj Dhawale(2016) “Performance of Piled Raft Foundation on Sand Bed” International Journal of Innovative  Research in Science, Engineering and Technology,(An ISO 3297: 2007 Certified Organization),Vol. 5, Issue 6, June 2016 Jaymin D. Patil,, Sandeep A. Vasanvala,, Chandresh H. Solanki(2016),“An Experimental Study on Behavior of Piled Raft  Foundation “Indian Geotechnical Journal, volume 46,issue 1 pp.16-24.
Raut J. M., Khandeshwar S. R. and Bajad S. P.,(2015), “Load Sharing Ratio of Piled Raft foundation”, Proceeding of 50th Indian  Geotechnical Conference, Paper No. 645, December 17-19, 2015.
Nitin Nandwani, Prof P.J.Salunke, Prof N.G.Gore(2015), “Comparative Study Of Piled Raft Foundation” International Journal Of  Engineering Sciences & Research Technology, ISSN: 2277-9655, Namdwani, 4(11): November, 2015,pp.60-64.
Jaymin D Patil, Sandeep A Vasanwala, Chandresh H Solanki (2014),” An Experimental Investigation On Behavior Of Piled Raft  Foundation”, International Journal of Geomatics and Geosciences Volume 5, No 2, 2014, ISSN 0976 – 4380, Pp.300-311.
Basuony El-Garhy, Ahmed Abdel Galil, Abdel-Fattah Youssef, Mohamed Abo Raia (2013), “Behavior of Raft on Settlement  Reducing Piles: Experimental Model Study “Journal Of Rock Mechanics And Geotechnical Engineering, Volume 5, Issue 5, Pp.389-399.
R. R. Chaudhari, Dr K. N. Kadam(2013), “Effect Of Piled Raft Design On High-Rise Building Considering Soil Structure  Interaction “International Journal Of Scientific & Technology Research Volume 2, Issue 6, June 2013 ISSN 2277-8616 72 Ijstr©2013.
Dr.G.Srilakshmi, Chethan Gowda R K(2012)” Analysis of Piled Raft Foundation by Finite Element Method”, Non-Circuit Branches  of the 3rd Nirma University International Conference on Engineering (NUiCONE 2012).
 Fioravante V., and Giretti D.,(2010), Contact versus Noncontact Piled Raft Foundations, Canadian Geotechnical Journal, 47(11), pp 1271-1287.