Notes About Bearing Capacity Equations
The results of soil bearing capacity equations need clarification regarding the value of the permissible bearing capacity.
The Terzaghi equation has been developed to calculate the bearing capacity of soil many times,
So we have many equations for both (Meyerhof, Hansen, Visk, and Terzaghi).
Each of these equations produces a different value as far as the bearing capacity of the soil,
but what raises suspicion is that sometimes the following occurs:
- Increasing the friction angle gives very significant results
- Increasing the width of the foundation also gives high results
The use of equations in the case of raft foundations leads, accordingly, to larger values in the bearing capacity of the soil, The truth is that these values demonstrate the soil’s bearing capacity to resist shear and not just the simple concept of top-down loading. There is no relation between these values and the settlement values. In other words, the bearing capacity of the soil cannot be estimated based on the calculations of these equations only, but they must be reviewed with the settlement values so that they are proportional to the value of the permissible bearing capacity.
Terzaghi’s assumptions must also be reviewed to achieve a greater understanding of this method for calculating soil bearing capacity. Also, in the case of clay soil, the results are often acceptable due to not taking into account the effect of foundation width.
Accordingly, in 1967, Terzaghi and Peck developed a method to calculate the bearing capacity of sandy soil based on a relationship between the number of SPT beats and the ratio between the depth to width of the foundation and the bearing capacity of the soil.
Which gives results at a value lower than the soil capacity equations and is somewhat acceptable for settlement but it may underestimate the soil capacity.
Engineer Mustafa Magdy
Bearing Capacity Excel Results
