Hansen’s bearing capacity theory
For cohesive soils, Values obtained by Terzaghi’s bearing capacity theory are more than the experimental values. But however it is showing same values for cohesion less soils. So Hansen modified the equation by considering shape, depth and inclination factors.
According to Hansen’s
qu = c’Nc Sc dc ic + Df Nq Sq dq iq + 0.5 B Ny Sy dy iy
Where Nc, Nq, Ny = Hansen’s bearing capacity factors
Sc, Sq, Sy = shape factors
dc, dq, dy = depth factors
ic, iq, iy = inclination factors
Bearing capacity factors are calculated by following equations.
For different values of Hansen bearing capacity factors are calculated in the below table.
Nc | Nq | Ny | |
0 | 5.14 | 1 | 0 |
5 | 6.48 | 1.57 | 0.09 |
10 | 8.34 | 2.47 | 0.09 |
15 | 10.97 | 3.94 | 1.42 |
20 | 14.83 | 6.4 | 3.54 |
25 | 20.72 | 10.66 | 8.11 |
30 | 30.14 | 18.40 | 18.08 |
35 | 46.13 | 33.29 | 40.69 |
40 | 75.32 | 64.18 | 95.41 |
45 | 133.89 | 134.85 | 240.85 |
50 | 266.89 | 318.96 | 681.84 |
Shape factors for different shapes of footing are given in below table.
Shape of footing | Sc | Sq | Sy |
Continuous
| 1 | 1 | 1 |
Rectangular
| 1+0.2B/L | 1+0.2B/L | 1-0.4B/L |
Square
| 1.3 | 1.2 | 0.8 |
Circular
| 1.3 | 1.2 | 0.6 |
Depth factors are considered according to the following table.
Depth factors | Values |
dc | 1+0.35(D/B) |
dq | 1+0.35(D/B) |
dy | 1.0 |
Similarly inclination factors are considered from below table.
Inclination factors | Values |
ic | 1 – [H/(2 c B L)] |
iq | 1 – 1.5 (H/V) |
iy | (iq)2 |
Where H = horizontal component of inclined load
B = width of footing
L = length of footing.