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14 - CPT Analysis

1.0 Introduction

This tutorial provides an introduction to the CPT interpretation analysis module in Settle3. Before proceeding with the tutorial, make sure you’ve gone through Tutorial 01 – Quick Start so you’re familiar with the product’s basic functions and features.

Topics Covered in this Tutorial:

  • CPT data interpretation

Finished Product:

The finished product of this tutorial can be found in the Tutorial 14 CPT Analysis.s3z file. All tutorial files installed with Settle3 can be accessed by selecting File > Recent Folders > Tutorials Folder from the Settle3 main menu.

2.0 Model

2.1 Project Settings

  1. Select Home > Project Settings project settings icon (CTRL + J) to open the Project Settings dialog.
  2. In the General tab, make sure the Units are set as Metric, stress as kPa.
  3. Go to the Cone Penetration Test (CPT) tab and check the CPT Analysis checkbox to turn the CPT analysis option on.
    Project Settings dialog
  4. Click OK to close the dialog and save your changes.
You may be warned that the unit system has changed. If this is the case, select Yes to reset the unit-dependent values.

3.0 Enter CPT Data

  1. Select CPT > Add CPT add cpt to open the CPT Input dialog.
  2. Click the Import button below the table and import the file CPT Input.txt which should be available in the tutorial folder.
  3. Edit CPT Data dialog

  4. The Import Data dialog will appear. You can check the 'Auto Detect Data' and the data will be imported as shown below:
    Import Data dialog
  5. Click OK to return to the previous dialog.
  6. Leave the GWT depth for correlations equal to 2 m.
  7. Keep the location to: x = 0 , y = 0. This will be where the CPT is put in the plan view of the model. The dialog should look as follows:
    Edit CPT Data dialog
  8. Click OK to close the dialog.
  9. Click on the left side of the screen to place the CPT anywhere in the Plan view.

4.0 Results Interpretation

  1. Right-click on the CPT point and select Graph CPT.

4.1 Tabular Results

Select the Results tab at the bottom of the Chart view. The default results shown are:

  • Corrected Cone Resistance, qt
  • Unit Weight,
  • Effective Overburden Stress, Effective Overburden Stress Symbol
  • Total Overburden Stress, Total Overburden Stress Symbol
  • Stress Normalized Cone Resistance, Qt1
  • Stress Normalized Friction Ratio, Fr
  • Soil Type Index, Ic
  • Normalized Pore Pressure, Bq
  • Equivalent SPT N60

For a full list of the tabulated results, see the CPT Analysis Results.

4.1.1 Editing the Displayed Columns

You can edit the column displayed in the results by clicking the Edit Column edit column icon icon in the toolbar.

Edit CPT Columns dialog

You can add any number of results to the Columns on display window. Just double click on the desired result in the Columns available to display window or select the desired results and use the Left Arrow Left arrow icon to move them over.

The items in the Columns on display window can then be rearranged by using the up and down up arrowdown arrow arrows.

You can also use the Match to Charts option to match the column data to the displayed graphs.

4.1.2 Exporting Tabular Results to Excel

For exporting tabular results to Excel, there are two options available under the Export Data to Excel export to excel icon icon.

  • Shown Data
  • All Data

With Shown Data, only the tabular results that are currently displayed will be exported. If you select All Data then all of the calculated CPT results will be exported.

4.2 Graphical Results

The data shown by default in the Inputs tab are:

  • Cone Resistance, qc
  • Sleeve Resistance, fs
  • Pore Pressure, u2

These charts cannot be manipulated.

The charts in any of the Results tabs though (by default, one is created), CAN be customized. The charts shown in the Results tab by default are:

  • Stress Normalized Cone Resistance
  • Stress Normalized Friction Ratio
  • Normalized Pore Pressure
  • Robertson 1986 SBT Chart classification

To get a full-screen view of the results graphs, click on View Mode view mode icon > Expand Chart View expand chart view icon

To reorder the charts, click on the Reorder Charts Chart with Numbered List icon icon.

CPT Chart Output dialog

In the CPT Chart Output dialog you’ll be able to:

  • Add Charts add
  • Delete Charts Cancel delete icon
  • Reorder Charts up arrowdown arrow
  • Reset the Charts to the defaults Reset icon

4.2.1 SPT Plots

  1. To view the SBT plots, click on the Plot SBT Zone plot spt icon. The following chart should appear:

SBT Zones dialog

Use the dropdown in the SBT Zones dialog to change the chart type. You can export and save the image using the Export Image option.

5.0 Advanced Topics

5.1 Soil Profile from CPT

This feature just shows a visualization of soil classification along the depth of CPT data. This data does not create soil profile in Sette3 model as it requires engineering judgement in terms of parameters required for settlement such as mv, Cc, Cr, etc from CPT data.
  1. Right-click on the CPT point and select CPT Soil Classification cpt soil classification icon.
    cpt soil profile
  2. You will be guided through the Soil Profile option.

    On the Soil Classification tab, you’ll see a breakdown of the soil types within each depth range. The method used can be changed using the CPT Options button. The predominant soil type will be used as the soil type for that depth range. You can change the size of the depth range using the Delta Size input. For now, leave the Delta Size equal to 1.
  3. Select the Soil Layers tab. The soil profile has now been determined using the Robertson 1986 method, with a Delta Size of 1m.
  4. You will see the merged soil layer column with the thickness of each soil layers defined as shown below.
    CPT Soil Profile dialog
  5. Click OK to Exit the dialog. Note this profile is only for visual purposes with CPT data input and soil classification. This soil profile is not used for the soil model in Settle3.
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