SI Units
The following program calculates the ultimate bearing capacity for a single pile. Point resistance and skin friction are the two components of pile bearing capacity.
Qu = Qpoint + Qskin
Input Design Parameters
Enter the diameter of the pile (d) m
Enter the depth of the pile (L) m
Enter the factor of safety with respect to bearing capacity (FS)
Enter the soil's undrained cohesion (Cu) kN/m2
Enter the depth of the ground water table (DGWT) m
Point Resistance
Qpoint = (cNc* + q'Nq*) A
Where c is soil cohesion (zero in the case of sand), q' is the vertical stress at pile tip, and Nc* and Nq* are bearing capacity factors.
For piles installed in cohesive soil, the general equation given above becomes Qpoint = (9 Cu ) A
Where Cu is the soil's undrained cohesion
For a circular pile:
the cross sectional area of the pile (A) m2
the point resistance of the pile (Qpoint) kN
Skin Friction
Qskin = S f DL p and f = a Cu
Where f is the coefficient of friction, DL is the length of the segment of the pile, p is the pile perimeter, a is the empirical adhesion factor, and Cu is the soil's undrained cohesion.
Use the chart or the table below to determine the value of a which corresponds to the soil cohesion entered above.
the undrained cohesion (Cu) kN/m2
Enter the value for a
the skin resistance of the pile (Qskin) kN
Total Bearing Capacity
the total ultimate bearing capacity of the pile (Qu) kN
the allowable bearing capacity of the pile (Qa) kN
Summary
input design parameters and outcome of the design of a single circular pile installed in cohesive soil
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Contact A. Ghaly at ghalya@union.edu
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Disclaimer: The author disclaims any and all responsibility for the application of stated principles, and shall not be liable for any loss or damage arising therefrom.