# Soil Behaviour Type Index

## Soil Behaviour Type Index 1

The soil behaviour type index ($\begin{array}{l}I_c\end{array}$) in Soil_Behaviour_Type_Index_1 is defined as:

$\begin{array}{l}I_c\end{array}$ is calculated using $\begin{array}{l}n=1\end{array}$, if $\begin{array}{l}I_c> I_{\text{c break}}\end{array}$, then it's been accepted, otherwise it's calculated using $\begin{array}{l}n=0.5\end{array}$. If $\begin{array}{l}I_c< I_{\text{c break}}\end{array}$ break then it's accepted, otherwise it's calculated using $\begin{array}{l}n=0.7\end{array}$.

Robertson and Wride (1998)

Where:

$\begin{array}{l}C_1\end{array}$ is 3.47 in the published formula, and is stored in the Soil_Behaviour_Type_Index_1_C1 field.
$\begin{array}{l}C_2\end{array}$is 1.22 in the published formula, and is stored in the Soil_Behaviour_Type_Index_1_C2 field.

The constants are stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

## Transition zones

A Trasition Zone in Soil_Behaviour_Type_Index_Transition_1 for a certain depth is considered when:
$\begin{array}{l}2.3< I_c< 2.9\end{array}$;
The rate of $\begin{array}{l}I_c\end{array}$ change is rapid (slope of $\begin{array}{l}I_c\end{array}$ vs. depth above and below of the current depth > 5)
and crosses the $\begin{array}{l}I_c=2.6\end{array}$ line.

## Soil Behaviour Type Index 2

The soil behaviour type index ($\begin{array}{l}I_c\end{array}$) in Soil_Behaviour_Type_Index_2 is defined as:

Jefferies and Davies (1993), NCHRP Synthesis 368 p 27

Where:
$\begin{array}{l}C_1\end{array}$ is 3 in the published formula, and is stored in the Soil_Behaviour_Type_Index_2_C1 field.
$\begin{array}{l}C_2\end{array}$ is 1.5 in the published formula, and is stored in the Soil_Behaviour_Type_Index_2_C2 field.
$\begin{array}{l}C_3\end{array}$ is 1.3 in the published formula, and is stored in the Soil_Behaviour_Type_Index_2_C3 field.

The constants are stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

## Soil Behaviour Type Index 3

The non-normalised Soil Behaviour Type Index ($\begin{array}{l}I_{SBT}\end{array}$) in Soil_Behaviour_Type_Index_3 is defined as:

Robertson (2010), CPT 10, paper 2-56 (http://www.cpt10.com/PDF_Files/2-56RobSBT.pdf)

Where:
$\begin{array}{l}C_1\end{array}$ is 3.47 in the published formula and is stored in the Soil_Behaviour_Type_Index_3_C1 field.
$\begin{array}{l}q_t\end{array}$ is taken from the Total_Cone_Resistance field on the CPT_DATA table.
$\begin{array}{l}q_c\end{array}$ is taken from the Cone_Resistance field on the CPT_DATA table.
$\begin{array}{l}p_a\end{array}$ is the Atmospheric pressure, 101.4 kPa, and is set in the Formula Tool.
$\begin{array}{l}R_f\end{array}$ is taken from the Friction_Ratio field on the CPT_DATA table.
$\begin{array}{l}C_2\end{array}$ is 1.22 in the published formula and is stored in the Soil_Behaviour_Type_Index_3_C2 field.

The constants are stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

## Soil Behaviour Type Index 4

The soil behaviour type index ($\begin{array}{l}I_c\end{array}$) in Soil_Behaviour_Type_Index_4 is defined as:

Been and Jefferies (1992), Soil liquefaction, a critical state approach, pp. 206-207

Where:
$\begin{array}{l}C_1\end{array}$ is 3 in the published formula, and is stored in the Soil_Behaviour_Type_Index_4_C1 field.
$\begin{array}{l}C_2\end{array}$ is 1.5 in the published formula, and is stored in the Soil_Behaviour_Type_Index_4_C2 field.
$\begin{array}{l}C_3\end{array}$ is 1.3 in the published formula, and is stored in the Soil_Behaviour_Type_Index_4_C3 field.

The constants are stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.