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 angle of shearing resistance (f) degrees
Enter the saturated unit weight of the sand (g sat) kN/m3
Enter the bulk unit weight of the sand (g bulk) kN/m3
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 cohesionless soil, the general equation given above becomes Qpoint = (q'Nq*)A
the vertical stress at pile tip (q') kN/m2
Use the chart or the table below to determine the value of Nq* which corresponds to the angle shearing resistance entered above.
Enter the value of Nq*
the ultimate stress at the pile tip (qpoint) kN/m2
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 = s'v k tan d
Where f is the coefficient of friction, DL is the length of the segment of the pile, p is the pile perimeter, k is the coefficient of lateral earth pressure, and d is the pile-soil friction angle.
the angle of shearing resistance f degrees
The pile-soil friction angle (d) varies between 0.5 f degrees and 0.8 f degrees
Enter the desired value of d degrees
The coefficient of lateral earth pressure (k) varies due to different methods of pile installation.
Enter the desired value of k
The effective vertical stress (s'v) increases along the pile depth up to a maximum limit (L') of 10 to 20 times the pile diameter (d), and then becomes constant.
Enter the factor for calculating L' (expressed in terms of pile diameter)
the length L' m
the depth of ground water table (DGWT) m
If DGWT < L', check here
If DGWT > L', check here
If DGWT = L', check here
the value of the effective stress at or above the GWT (s'v1) kN/m2
the value of the effective stress at depth L' (s'v2) kN/m2
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 cohesionless soil
Copyright 1999-2024 A. Ghaly. All rights reserved.
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.