{{error}}

{{tabaka.z | round:0}}

{{tabaka.z1 | round:2}}

{{tabaka.h | round:2}}

{{error}}

{{a | round:0}}

{{a| round:3}}

{{a| round:3}}

{{a| round:3}}

The calculation tool given above for calculating average c-φ for layered soils follows the procedure given in "Foundation Analysis and Design, 5th Edition (Joseph E. Bowles) - Chapter 4. The details, formulations and procedure of the calculations are given below.

The average cohesion and internal friction angle of the soil profile is calculated as follows:

$$c_{av} = {c_1H_1 + c_2H_2 + c_3H_3 + ...+c_nH_n \over \sum H_i} $$

$$\phi_{av} = tan^{-1}\left({H_1tan\phi_1 + H_2tan\phi_2 + H_3tan\phi_3 + ...+H_ntan\phi_n \over \sum H_i}\right) $$

Where;

c_{av}: Average cohesion of entire soil profile

φ_{av}: Average friction angle of entire soil profile

c_{i}: Cohesion of single soil layer

φ_{i}: Friction angle of single soil layer

H_{i}: Thickness of single soil layer

The effective shear depth is approxiamtely:

$$H_e = 0.5Btan(45+\phi/2) $$

Where;

B: Foundation width

φ: Friction angle of the soil layer under the foundation

Firstly, H_{e} is calculated using the friction angle of the soil layer just under the foundation to determine the contributing soil layers. After that, using the formulations given above and the c-φ values of the soil layers
inside the effective shear zone(H_{e}), first set of c_{av} and φ_{av} vaules are calculated (Iteration-0).

Secondly, another H_{e} is calculated using the φ_{av} value calculated in iteration-0. Using the new H_{e}, a new set of c_{av} and φ_{av} are calculated (Iteration-1).

The c_{av} and φ_{av} values calculated in the last iteration are the final results. These values can be used in a bearing capacity calculation of a shallow foundation sitting on a layered soil. Bearing capacity of a
shallow foundation can be calculated using Terzaghi(1943) and Meyerhof(1963) methods.