Page 49 - Unit2.docx

a i = adhesion factor for earth layer

c udci = undrained shear strength of clay.

A mi = area of pile shaft in contact with the soil.

The adhesion factor α is taken as 0 for the firs three meters where it is expected
hole room and fill material or week strata. For piles with constant cross-sectional
area the value of α can be taken as 2.0 and for piles with uniform cross-sectional
growth the value of α can be taken as 2.2 .

Figure 5-2 Cohesion Pile
© It's Engg. Life
Example 5.3

28 m wood pile is installed small end down in clay. Pile diameter is 225 mm at the
end and 20 mm/m increase in diameter. The undrained shear strength of the soil,
measured from the pile cut-off level is: 0-6 m = 22 kP 6-22 m = 26 kPa 22-28 m =
29 kPa. Determine the ultimate load capacity of the pile. Pile cut-off level is 2.5m

from the ground level. γ Rd = 2.7

Figure 5-3 Example 5-3