This example shows the calculation of pile capacity in Bangkok clays. The designed pile is a bored pile diameter of 0.5 m with pile tip at -21.5 m. The pile cut-off level is at -1.50 m from the original ground (OG).
Soil profile in GEO5
The calculation is performed by spreadsheet pile_in_clay.xlsx and compared with GEO5: PILE software.
Nc value = 9 (NAVFAC DM7-02) is used in this calculation, while the alpha value is obtained from Sambhandaraksa and Pitupakorn (1985); see Fig.4 below. It is common to use Nc = 9 for stiff clay layers with Su greater than 100 kPa.
The correlation between SPT-N value and unconfined compressive strength (2Su) for cohesive soils as shown in table 2.6 (Teng, 1962). It was noted that those relationships for cohesive soil are not reliable. It is urged to conduct soil testing for any large project.
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REFERENCES
NAVFAC DM 7-02, Foundations and Earth Structures, Naval Facilities Engineering Command
Sambhandaraksa, S., and Pitupakorn, W. (1985). "Prediction of prestressed concrete pile capacity in stiff clay and clayey sand," Proc. of 8th Southeast Asian Geotechnical Conference, Kuala Lumpur, Malaysia, 3.58-3.63.
WC Teng, Foundation Design, Prentice-Hall, 1962