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Author:
M. Z. Ahmed
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2001-08-25 |
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We have a project where H piles will be driven through a deposit of 7m thick calcerous sand. This material is found between 3 to 10m depth below the grade. I would like to know about the following:
1) Effect of driving through calcareous sands on skin friction.
2) Driving resistance.
3) Set up factor.
4) In the calculation of skin friction whether the k(lateral earth pressure) and f(coefficient of friction) values shall be reduced.
Regards,
AHMED
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Follow-up:
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Author:
Tom Sklucki
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2001-09-06 |
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A useful starting point is H.G. Poulos' book 'Marine Geotechnics' Unwin Hyman Ltd., London, 1988
ISBN 0-04-620024-X. This discusses properties of calcareous soils and effects on skin friction and end bearing, also cyclic degradation due to wave loading.
For piling a useful references from the book appears to be
Nauroy JF, Brucy F, Le Tirant P, and Kervadec J-P (1986)
Design and installation of piles in calcareous formations
Proc. 3rd Int. Conf. Numerical Methods in Offshore Piling, Nantes
pp 461-480
Much of the experience with calcareous silts & sands has been offshore in Australia (Bass Straight or North-West Shelf) - see Proc Int Conf on Calcareous Sediments Perth 1988, Florida/Caribbean or the Gulf (Arabian/Persian). There is also some work in Israel & Egypt.
I came across the problem in connection with offshore work for Mobil and Amoco in the Gulf of Suez where calcareous sands & gravels, the product of degraded coral deposits, were associated with buried intact coral masses.
You may experience high and very variable driving resistances. Skin friction may be low.
Calcareous sands are often cemented to some degree and then have a brittle structure. Driving piles into this can leave an annular void around the pile so it is often wise to be cautious about the degree of lateral restraint and skin friction in the upper part of the embedment.
Tomlinson MJ (2000) Foundation Design and Construction 7th Edition, Pearson (Prentice Hall), Harlow Essex ISBN 0-13-031180-4 quotes a paper by Poulos which gives a skin friction between 5 and 10 percent of the effective overburden pressure for driven piles (between 50 and 80 percent with a limiting value between 60 kPa and 100 kPa for bored piles).
There is some comment about skin grouting to radically improve the pile/soil interface friction in Tomlinson MJ (1994) Pile Design and Construction Practice, 4th Edition, Spon, London ISBN 0-41-918450-3
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Follow-ups:
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Subject:
Piles in Calcerous Sand 