23 March 2017

Hansen’s bearing capacity theory

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
q= c’NSc dc ic + image Df Nq Sq dq iq + 0.5 image B NSy 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.
Bearing capacity factors calculation formula
For different values of image Hansen bearing capacity factors are calculated in the below table.
imageNcNqNy
05.1410
56.481.570.09
108.342.470.09
1510.973.941.42
2014.836.43.54
2520.7210.668.11
3030.1418.4018.08
3546.1333.2940.69
4075.3264.1895.41
45133.89134.85240.85
50266.89318.96681.84

Shape factors for different shapes of footing are given in below table.
Shape of footingScSqSy
Continuous
111
Rectangular
1+0.2B/L1+0.2B/L1-0.4B/L
Square
1.31.20.8
Circular
1.31.20.6
Depth factors are considered according to the following table.
Depth factorsValues
dc1+0.35(D/B)
dq1+0.35(D/B)
dy1.0
Similarly inclination factors are considered from below table.
Inclination factorsValues
ic1 – [H/(2 c B L)]
iq1 – 1.5 (H/V)
iy(iq)2
Where H = horizontal component of inclined load
B = width of footing
L = length of footing.

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