Preconsolidation Stress and Overconsolidation Ratio

Preconsolidation Stress 1 and Overconsolidation Ratio 1

The Preconsolidation Stress 1 ( $\begin{array}{l}\sigma_p'\end{array}$ ) of clay in Preconsolidation_Stress_1 is defined as:

$\begin{array}{l}\displaystyle \sigma'_p=C_1\cdot (q_t-\sigma_{v0})\end{array}$

Mayne (1995), Demers and Leroueil (2002), NCHRP Synthesis 368 p 34

Where:
$\begin{array}{l}C_1\end{array}$ is 0.33 in the published formula, and is stored in the Preconsolidation_Stress_1_C1 field.

The constant is stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

The overconsolidation ratio 1 in Overconsolidation_Ratio_1 is defined as:

$\begin{array}{l}\displaystyle OCR=\frac{\sigma'_p}{\sigma'_{v0}}\end{array}$

$\begin{array}{l}\sigma'_p\end{array}$ is taken from Preconsolidation_Stress_1 field

Preconsolidation Stress 2 and Overconsolidation Ratio 2

The Preconsolidation Stress 2 ( $\begin{array}{l}\sigma_p'\end{array}$ ) of clay in Preconsolidation_Stress_2 is defined as:

$\begin{array}{l}\displaystyle \sigma'_{p}=C_1 \cdot \Delta u\end{array}$

Chen and Mayne (1996), NCHRP Synthesis 368 p 34

Where:
$\begin{array}{l}C_1\end{array}$ is 0.53 in the published formula, and is stored in the Preconsolidation_Stress_2_C1 field.

The constant is stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

The overconsolidation ratio 2 in Overconsolidation_Ratio_2 is defined as:

$\begin{array}{l}\displaystyle OCR=\frac{\sigma'_p}{\sigma'_{v0}}\end{array}$

Where:

$\begin{array}{l}\sigma'_p\end{array}$ is taken from Preconsolidation_Stress_2 field

Preconsolidation Stress 3 and Overconsolidation Ratio 3

The Preconsolidation Stress 3 ( $\begin{array}{l}\sigma_p'\end{array}$ ) of clay in Preconsolidation_Stress_3 is defined as:

$\begin{array}{l}\displaystyle \sigma'_{p}=C_1 \cdot(q_t-u_2)\end{array}$

Mayne (2005), NCHRP Synthesis 368 p 35

Where:
$\begin{array}{l}C_1\end{array}$ is 0.6 in the published formula, and is stored in the Preconsolidation_Stress_3_C1 field.

The constant is stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

The overconsolidation ratio 3 in Overconsolidation_Ratio_3 is defined as:

$\begin{array}{l}\displaystyle OCR=\frac{\sigma'_p}{\sigma'_{v0}}\end{array}$

Where:

$\begin{array}{l}\sigma'_p\end{array}$ is taken from Preconsolidation_Stress_3 field

Preconsolidation Stress 4 and Overconsolidation Ratio 4

The Preconsolidation Stress 4 ( $\begin{array}{l}\sigma_p'\end{array}$ ) of clay in Preconsolidation_Stress_4 is defined as:

$\begin{array}{l}\displaystyle \sigma'_p=C_1 \cdot Q_t^{C_2}\cdot \sigma'_{v0}\end{array}$

Robertson (2009), Guide to CPT p 31

Where:
$\begin{array}{l}C_1\end{array}$ is 0.25 in the published formula, and is stored in the Preconsolidation_Stress_4_C1 field
$\begin{array}{l}C_2\end{array}$ is 1.25 in the published formula, and is stored in the Preconsolidation_Stress_4_C2 field

The constant is stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

The overconsolidation ratio 4 in Overconsolidation_Ratio_4 is defined as:

$\begin{array}{l}\displaystyle OCR=\frac{\sigma'_p}{\sigma'_{v0}}\end{array}$

Where:

$\begin{array}{l}\sigma'_p\end{array}$ is taken from Preconsolidation_Stress_4 field

Preconsolidation Stress 5 and Overconsolidation Ratio 5

The Preconsolidation Stress 5 ( $\begin{array}{l}\sigma_p'\end{array}$ ) of sand in Preconsolidation_Stress_5 is defined as:

$\begin{array}{l}\displaystyle \sigma'_p=\left[ \frac{C_1 \cdot(q_t/\sigma_{atm})^{C_2}} {(1-sin\Phi')\cdot(\sigma'_{v0}/\sigma_{atm})^{C_3} }\right]^{\frac{1}{sin\Phi'-C_4}}\cdot\sigma'_{v0}\end{array}$

Mayne (2005), NCHRP Synthesis 368 p 35

Where:
$\begin{array}{l}C_1\end{array}$ is 0.192 in the published formula, and is stored in the Preconsolidation_Stress_5_C1 field
$\begin{array}{l}C_2\end{array}$ is 0.22 in the published formula, and is stored in the Preconsolidation_Stress_5_C2 field
$\begin{array}{l}C_3\end{array}$ is 0.31 in the published formula, and is stored in the Preconsolidation_Stress_5_C3 field
$\begin{array}{l}C_4\end{array}$ is 0.27 in the published formula, and is stored in the Preconsolidation_Stress_5_C4 field
$\begin{array}{l}\Phi'\end{array}$ is taken from Friction_Angle_3

The constants are stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

The overconsolidation ratio 5 in Overconsolidation_Ratio_5 is defined as:

$\begin{array}{l}\displaystyle OCR=\frac{\sigma'_p}{\sigma'_{v0}}\end{array}$

Where:

$\begin{array}{l}\sigma'_p\end{array}$ is taken from Preconsolidation_Stress_5 field

Preconsolidation Stress 6 and Overconsolidation Ratio 6

The Preconsolidation Stress 6 ( $\begin{array}{l}\sigma_p'\end{array}$ ) of all soil types in Preconsolidation_Stress_6 is defined as:

$\begin{array}{l}\displaystyle \sigma'_p=C_1 \cdot \sigma_{atm}^{C_2} \cdot (G_0)^{C_3} \cdot \sigma_{v0}'^{C_4}\end{array}$

Mayne (2007), NCHRP Synthesis 368 pp 37

Where:
$\begin{array}{l}\sigma'_p\end{array}$ , $\begin{array}{l}\sigma_{atm}\end{array}$ , $\begin{array}{l}G_0\end{array}$ and $\begin{array}{l}\sigma'_{v0}\end{array}$ are in kPa
$\begin{array}{l}C_1\end{array}$ is 0.101 in the published formula, and is stored in the Preconsolidation_Stress_6_C1 field
$\begin{array}{l}C_2\end{array}$ is 0.102 in the published formula, and is stored in the Preconsolidation_Stress_6_C2 field
$\begin{array}{l}C_3\end{array}$ is 0.478 in the published formula, and is stored in the Preconsolidation_Stress_6_C3 field
$\begin{array}{l}C_4\end{array}$ is 0.420 in the published formula, and is stored in the Preconsolidation_Stress_6_C4 field
$\begin{array}{l}G_0\end{array}$ is taken from Small_Strain_Shear_Modulus_2

The constants are stored on CPT_POINT_CORRELATION_PARAMETERS and CPT_PROJECT_CORRELATION_PARAMETERS tables.

The overconsolidation ratio 6 in Overconsolidation_Ratio_6 is defined as:

$\begin{array}{l}\displaystyle OCR=\frac{\sigma'_p}{\sigma'_{v0}}\end{array}$

Where:

$\begin{array}{l}\sigma'_p\end{array}$ is taken from Preconsolidation_Stress_6 field

On this page