SPT N60 Value

SPT N60 Value 1

The $//<![CDATA[ \begin{array}{l}SPT N_{60}\end{array} //]]>$ in SPT_N60_1 is defined as:

$$//<![CDATA[ \begin{array}{l}\displaystyle N_{60}=\frac{q_c}{C_1 \cdot p_a(1-\frac{I_c}{C_2}})\end{array} //]]>$$

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

Where:
     $//<![CDATA[ \begin{array}{l}C_1\end{array} //]]>$ is 8.5 in the published formula, and is stored in the SPT_N60_1_C1 field.
     $//<![CDATA[ \begin{array}{l}C_2\end{array} //]]>$ is 4.6 in the published formula, and is stored in the SPT_N60_1_C2 field.
     $//<![CDATA[ \begin{array}{l}p_a\end{array} //]]>$ is the Atmospheric pressure, 100 kPa, and cannot be changed in the CPT Tool.
     $//<![CDATA[ \begin{array}{l}I_c\end{array} //]]>$ 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 $//<![CDATA[ \begin{array}{l}SPT N_{60}\end{array} //]]>$ in SPT_N60_2 is defined as:

$$//<![CDATA[ \begin{array}{l}\displaystyle N_{60}=\frac{q_c}{C_1 \cdot (1- \frac{I_c}{C_2})}\end{array} //]]>$$

Jefferies and Davies (1993)

Where:
     $//<![CDATA[ \begin{array}{l}C_1\end{array} //]]>$ is 0.85 in the published formula, and is stored in the SPT_N60_2_C1 field.
     $//<![CDATA[ \begin{array}{l}C_2\end{array} //]]>$ is 4.75 in the published formula, and is stored in the SPT_N60_2_C2 field.
     $//<![CDATA[ \begin{array}{l}I_c\end{array} //]]>$ 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.