### Earthquake Influence on Bearing Capacity of Foundation Soil (Part-2)

Now we will see the basic equation provided by Terzaghi. Here the equation is given for unit foundation length.

At first we provide the parameter used in this expression:

Q=bearing capacity of soil

B=foundation width

C=cohesion of soil

ϒ=unit weight of soil

Df=depth of foundation
These factors used in bearing capacity expression may be modified using following table:
Where k=0 in case of bearing capacity factors provided by Terzaghi.

As an example:

Let consider, c=200 lb/ft2
Φ=300

B=5 ft

Df=3 ft

Qstatic=5(200X36 + 112X3X22 + 112X5X20)

=100960 lbs/ft of unit foundation length

If earthquake hazard provides k=0.2 then

Qearthqauke=5(200X17 + 112X3X7 + 112X5X4)

=34360 lbs/ft of unit foundation length

From this example we can conclude a considerable reduction in ultimate bearing capacity of foundation soil is occurred on account of earthquake event.

Earthquake Influence on Bearing Capacity of Foundation Soil (Part-1)

#### 1 comment:

1. I 'm surprised at the above eqn.
Terzagi Bearing Capacity eqn as given in Bowles book, Foundation Analysis & Design, states:

q ult = CNc.Sc + qNq +.5gamma.B.Ngamma.Sgamma

which is different than the quantity between brackets in the above eqn!