Welcome to the Getting Started with GeoStudio video series.
This tutorial guides new users through the basics of creating a simple stress and deformation analysis in SIGMA/W.
This video will cover how to:
set up the properties of a SIGMA/W analysis in the Definition view;
use the Solve Manager to solve the numerical analysis;
interpret the solved analysis in Results View;
and view and print the analysis in Page Layout mode.
The project definition involves selecting the basic analysis properties,
drawing the model geometry,
creating and assigning material properties,
and defining the boundary and initial conditions.
This tutorial considers the change in stress and deformation of a geologic system
following the placement of a circular tank on the ground surface.
The underlying soil comprises two materials.
The system is symmetric about a central axis; therefore, the axisymmetric geometry definition will be used.
We will begin on the GeoStudio start page.
Here you can create a new project, open an existing project,
or click on the appropriate links to view the examples, tutorial videos, or engineering books
for each GeoStudio product available on the GEO-SLOPE website.
When creating a new project, you can select the default units and project page size from a range of standard sizes.
After clicking on the New button,
I will select the metric units with the letter-sized page and create an analysis.
Once the new project is created, the Define Analyses window opens where we can edit the analysis tree title,
specify the author, or add comments for future viewers.
Under the Settings tab, we can change the system of units and set a project start date.
We will add a Load/Deformation SIGMA/W analysis to the analysis tree and change its name to Tank Load.
We may also change the analysis type if desired,
or add a description about the analysis to help future users.
In the Settings tab, we can specify from where the initial stress conditions come.
Similarly, we can select the initial pore water pressure conditions from the parent analysis,
another GeoStudio analysis, a piezometric line, or a spatial function.
For the purposes of this analysis, we will not specify any initial pore water pressure or stress conditions.
Under the Convergence tab, we can change the convergence settings,
including the maximum number of iterations and the iteration comparison criteria.
We will use the default settings for this analysis.
More information on the convergence criteria is available in the SIGMA/W engineering book or the online help.
The Time tab can be used to change the number of load steps in the analysis.
Keep in mind that unlike a coupled consolidation analysis,
time duration does not affect a load-deformation analysis.
Only the number of load steps matter for load- deformation.
Again, we will use the default settings, which result in the load being applied in one step.
We are currently in the Definition view of our analysis.
The red and green lines in the model space represent the x and y axes, respectively,
and the grid is activated.
Both of these may be turned off by going to View | Grid.
The grid spacing and snap-to-grid option may also be modified here.
Since our problem is symmetric about a central angle, we will go to Define Geometry Properties and select the axisymmetric geometry option.
The central angle should be 360° such that the analysis computes the results for a full rotation about the central axis.
The base units of the analysis are found under View | Units.
Both the base units and the derived units may be modified.
However, we will use the default units for this analysis.
The zoom options along the bottom bar of the screen provide various options for adjusting the analysis view.
We can also go to View | Zoom, to change the display scale and current zoom percentage, or zoom to the extents of the model domain.
We can add axes to the working area to help visualize the drawing extents of our domain.
Under Sketch Axes, we will specify the titles for each axis, as well as the x and y axes extents.
The x axis minimum and maximum will be -5 m and 40 m, respectively,
and the y axis minimum and maximum will be -2 m and 26 m.
You can also modify the axis increments by toggling off the auto increment size button and changing the increment size for each axis.
Let us now set up the domain geometry.
There are several methods for drawing the model domain.
First of all, we may import regions from DWG or DXF files or from other GeoStudio files,
by going to File | Import Regions.
We may also import a drawing under Sketch Pictures, scale the drawing to the model domain,
and use it as a reference for creating the desired regions.
Alternatively, we can copy point coordinates from another GeoStudio file
or from spreadsheet software like Microsoft Excel,
and paste them into the Define Points window.
Finally, we can draw regions by going to Draw Regions.
Let us use this last option for defining our domain geometry.
In the Draw Degions window, ensure the polygonal region type is selected.
Points are automatically generated when we click on the working area
and lines are created between these points.
We may also enter point coordinates in the coordinate entry box at the bottom of the window.
To stop the Draw Regions command, click the right mouse button or press Esc.
The created region represents the bottom material.
We will use the same method to generate the overlying material.
In this analysis we expect that the largest deformations will occur beneath the tank.
For finite element analyses, a finer mesh is desirable in regions of the domain with greater gradients.
Thus, we wish to divide each soil layer into two so that the mesh discretization may be different below the tank.
To do so, select the Split Regions tool and draw a vertical line through the existing domain at x = 10 m.
After hitting Esc to stop the Split Regions command, we can see that the two original regions were each split into two,
given the addition of three points and two lines.
Additional points can be added to the domain if required.
We will add a point along the ground surface line indicating the outer circumference of the water tank.
The Sketch tools may be used to draw geometric shapes to help us visualize various aspects of our problem.
For example, we can use the Sketch Polylines button to draw the tank.
These sketches are not included in the domain or the analysis, and can be moved, modified or deleted using the Modify Objects command.
After defining the model geometry, the next step is to create and assign the material properties.
To establish the material, we will go to Define Materials.
We will click on the Add button to create a new material,
give this material a name,
and select the Total Stress Parameters material category from the first dropdown menu.
We will use the Linear Elastic material model, which is the default selection under the second dropdown menu.
For this material model, only the stiffness modulus and Poisson's ratio are required.
We will enter an E-modulus of 3000 kPa,
and a Poisson's ratio of 0.45.
The lower material will use the same material models as the upper soil,
so to create the second material, press the arrow on the Add button and select Clone.
Let us change the name of this new material
and adjust its properties such that the E-modulus is 4000 kPa.
The Poisson's ratio will remain the same for the lower material.
The material definition for our domain is complete so we can close the Define Materials window.
Now we will add the materials to our domain by going to Draw Materials,
selecting the Upper Layer material,
and clicking on the top two regions.
We will do the same for the lower two regions.
We may add a material table to our analysis by opening the Sketch Text dialogue and selecting the Insert Field option.
This opens an additional window where we can select which materials and properties we wish to include in the inserted text.
The 'Show as a table' option is already toggled on so we will press Insert.
The field representing the material table appears in the Sketch Text dialogue.
We may now click in the model space to indicate where we want the table to appear.
The table may be moved using the Modify Objects command.
Creating and assigning boundary conditions is very similar to creating and assigning material properties.
Under Define Boundary Conditions, we see that three boundary conditions are automatically generated.
These are the Fixed Y, Fixed X/Y, and Fixed X boundary conditions, which prohibit displacement in the specified directions.
In addition to these three, we need to add a new stress boundary condition to represent the pressure of the tank on the ground surface.
We will select the X-Y Stress type boundary condition and specify a constant y-stress of -40 kPa.
The negative sign indicates that the pressure is applied downward on the soil surface.
Now we can open the Draw Boundary Conditions window.
We will select the Fixed X boundary condition and apply it to the left and right boundaries.
Vertical displacements are allowed on these boundaries, while horizontal movement is restricted.
For the bottom boundary, we will assume that there are no horizontal or vertical displacements
and so we will apply the Fixed XY boundary condition along this line.
Finally, we will apply the Tank Pressure boundary condition to the line representing the contact between the ground surface and the tank bottom.
The last step of developing our numerical analysis is to view the finite element mesh by going to Draw Mesh Properties.
Here we can see that the default mesh is set to have an approximate global element size of 5 m.
We will change the global element size to 2 m.
If we hold down the CTRL button and select the two regions immediately below the tank, we can change the mesh properties of both regions.
We will change the element edge length by selecting the Ratio of Default Size option and entering a value of 0.5.
This decreases the mesh size such that it is half the global element size.
For these two regions, we will also apply secondary nodes so that eight-noded elements are used.
The remaining regions will have elements with four nodes.
In general, secondary nodes should be used for most stress-strain analyses.
Now we will ensure the analysis is activated in the Solve Manager window and solve the analysis by clicking on the Start button.
When solved, the window will automatically change to the Results view.
The Results Times window provides a list of the solved load steps.
In this case, we apply the tank load in a single step so there is only one load step available.
The deformed mesh automatically appears in the Results view.
We can change the properties of the deformed mesh in the Draw Vectors dialogue.
Instead of the deformed mesh, vectors can be used to view the simulated displacement.
The maximum displacement is provided in this window.
We can easily turn off the displacement visualization in the View Preferences toolbar along the right side of the screen,
or by going to View Preferences.
We may add contours to the domain by selecting a contour type from the dropdown menu.
The contour options are available in the Draw Contours dialogue.
Here we can add new contours,
change the contour increments,
add or remove a legend, and change the contour color scheme.
Contour labels may be added by selecting Draw Contour Labels and clicking on the desired contour.
The label disappears when we click on the contour a second time.
An alternative method for viewing SIGMA/W results is to create a Mohr circle by going to Draw Mohr circles
and selecting a node or Gauss region where we would like to know more about the stress results.
For example, when we select a node beneath the tank,
the Mohr circle is drawn based on the stresses at that node.
This information can be copied and pasted into another program or printed from this window.
The Draw Graph window offers a wide range of options for plotting the model results.
We can add a new graph for the vertical displacement beneath the tank.
In the dropdown menus, select Displacements,
Y-Displacement, vs. Y coordinate.
We will then click on Set Locations to choose which nodes to plot the results from.
If we change the select option to Geometry Items,
we can choose a region, line, or point.
Multiple geometry items may be selected by holding down the CTRL button while clicking on the left mouse button.
If we use the Custom Locations selection option, we can choose any node within the domain.
We will select the nodes along the left boundary of the domain by holding down the left mouse button
and dragging a box across the desired nodes.
For this plot, it makes more sense to plot the y coordinate along the y axis.
To do so, press the More button,
go to Options, and select the 'Rotate 90 degrees' option.
In the Graph Options window, we can also customize the labels,
change the scale of each axis,
add or remove the legend,
or change the line style.
After closing this window, we can see that the y coordinate is on the y axis and that the greatest negative or downward displacements
occur at the top of the soil, with decreasing displacement toward the bottom of the domain.
We can also use the More button to:
copy the graph as an image so it can be pasted as a picture in another program,
copy the graph data as tab-delimited columns, which can be pasted into other software like Microsoft Excel,
or export the data to a comma-delimited file.
There are other options available for viewing result information.
View Object Information provides information on each geometry item,
such as the boundary conditions applied to a line or the mesh properties of a region.
View Result Information provides details for a node or Gauss region.
This information includes coordinates, stresses, strains, material properties, and convergence results,
which can be useful when evaluating or comparing results from specific nodes within the domain.
Finally, a report of the analysis may be generated by going to View Report.
The report is an HTML format file summarizing the input data, domain geometry,
and other information from the analysis.
If at any time you are unsure in your understanding of a dialogue box,
select the Help tab or press F1 on your keyboard to access the online help.
If at any time you would like to view the engineering book for the product you are using
and do not want to return to the GeoStudio start page,
you can simply click on the Home button in the online help.
Once we are finished interpreting the results, we can turn on the Page Layout layer to set up the printing properties of the project file.
The Page Layout toolbar allows for the selection of the paper size, margins, and orientation;
the portion of the page in which the model appears called the viewport;
and the positioning and size of the model within the viewport.
We may also create, modify, or import a printing template.
A basic template was created when we selected the page size while setting up our project file at the beginning of this tutorial.
That concludes our Getting Started with SIGMA/W tutorial video.
Not all of the powerful features of SIGMA/W have been used or discussed here.
Please see the online help, supporting documentation for SIGMA/W and other tutorial videos
available on the GEOSLOPE website for more information.
Thank you for watching.