SPT N60 Value

SPT N60 Value 1

The $\begin{array}{l}SPT N_{60}\end{array}$ in SPT_N60_1 is defined as:

$\begin{array}{l}\displaystyle N_{60}=\frac{q_c}{C_1 \cdot p_a(1-\frac{I_c}{C_2}})\end{array}$

Robertson and Wride (1998), CPT in Geotechnical Practice p 151

Where:
$\begin{array}{l}C_1\end{array}$ is 8.5 in the published formula, and is stored in the SPT_N60_1_C1 field.
$\begin{array}{l}C_2\end{array}$ is 4.6 in the published formula, and is stored in the SPT_N60_1_C2 field.
$\begin{array}{l}p_a\end{array}$ is the Atmospheric pressure, 100 kPa, and cannot be changed in the CPT Tool.
$\begin{array}{l}I_c\end{array}$ is stored in the Soil_Behaviour_Type_Index_1 field.

The constants are stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

SPT N60 Value 2

The $\begin{array}{l}SPT N_{60}\end{array}$ in SPT_N60_2 is defined as:

$\begin{array}{l}\displaystyle N_{60}=\frac{q_c}{C_1 \cdot (1- \frac{I_c}{C_2})}\end{array}$

Jefferies and Davies (1993)

Where:
$\begin{array}{l}C_1\end{array}$ is 0.85 in the published formula, and is stored in the SPT_N60_2_C1 field.
$\begin{array}{l}C_2\end{array}$ is 4.75 in the published formula, and is stored in the SPT_N60_2_C2 field.
$\begin{array}{l}I_c\end{array}$ is stored in the Soil_Behaviour_Type_Index_2 field.

The constants are stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

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