Angle of Friction

Angle of Friction 1

The angle of internal friction of mixed soils ( $\begin{array}{l}\Phi'\end{array}$ ) in Friction_Angle_1 is defined as:

$\begin{array}{l}\displaystyle \Phi'=C_1º\cdot B_q^{C_2} \cdot [C_3+C_4 \cdot B_q+logQ_t]\end{array}$

Mayne and Campanella (2005), NCHRP Synthesis 368 pp 38-39

Where:
$\begin{array}{l}C_1\end{array}$ is 29.5 in the published formula, and is stored in the Friction_Angle_1_C1 field.
$\begin{array}{l}C_2\end{array}$ is 0.121 in the published formula, and is stored in the Friction_Angle_1_C2 field.
$\begin{array}{l}C_3\end{array}$ is 0.256 in the published formula, and is stored in the Friction_Angle_1_C3 field.
$\begin{array}{l}C_4\end{array}$ is 0.336 in the published formula, and is stored in the Friction_Angle_1_C4 field.

This correlation of $\begin{array}{l}\Phi'\end{array}$ is only applicable for $\begin{array}{l}0.1 < B_q< 1.0\end{array}$ and hence will only be calculated if $\begin{array}{l}B_q\end{array}$ in the Pore_Pressure_Ratio field on the same row lies within this range.

Angle of Friction 2

The angle of internal friction of sands ( $\begin{array}{l}\Phi'\end{array}$ ) in Friction_Angle_2 is defined as:

$\begin{array}{l}\displaystyle \Phi'=tan^{-1} \left (C_1+C_2 \cdot log \left( \frac{q_t}{\sigma'_{v0}} \right) \right)\end{array}$

Robertson and Campanella (1983), NCHRP Synthesis 368 p 38

Where:
$\begin{array}{l}C_1\end{array}$ is 0.1 in the published formula, and is stored in the Friction_Angle_2_C1 field.
$\begin{array}{l}C_2\end{array}$ is 0.38 in the published formula, and is stored in the Friction_Angle_2_C2 field.

This correlation of $\begin{array}{l}\Phi'\end{array}$ is only applicable for Sands and hence will only be calculated if the Soil_Type_1 field value is coarse or mixed.

Angle of Friction 3

The angle of internal friction of sand ( $\begin{array}{l}\Phi'\end{array}$ ) in Friction_Angle_3 is defined as:

$\begin{array}{l}\displaystyle \Phi'=C_1+C_2 \cdot log(q_{t1})\end{array}$

Kulhawy and Mayne (1990), NCHRP Synthesis 368 p 38

Where:
$\begin{array}{l}C_1\end{array}$ is 17.6° in the published formula, and is stored in the Friction_Angle_3_C1 field.
$\begin{array}{l}C_2\end{array}$ is 11.0° in the published formula, and is stored in the Friction_Angle_3_C2 field.

This correlation of $\begin{array}{l}\Phi'\end{array}$ is only applicable for Sands and hence will only be calculated if the Soil_Type_1 field value is coarse or mixed.

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