Table 7

Estimated nominal geotechnical resistance

Soil stratumSoil descriptionStratum thickness: feet (m)Average SPT N value: blows/foot or blows/305 mmEstimated unit nominal resistance for friction pile: kips/foot (kN/m)
1Soft silty clay6 (1·8)40·8 (11·7)
2Silty sand9 (2·7)61·2 (17·5)
3AFirm glacial clayWithin 30 feet (9·1 m) of natural ground elevation8 (2·4)112·8 (40·9)
3B More than 30 feet (9·1 m) below natural ground elevation65 (19·8)123·2 (46·7)

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