A slip center grid is used to generate the slip circles used in the critical surface search when the Surface Type = Circular, and the Search Method = Grid Search, in the Surface Options dialog. Each individual slip center in a grid represents the geometric center of a series of circles, determined according to the current Slope Limits or focus object, and the Radius Increment. This is described in the Grid Search topic.
The Add Grid option in the Surfaces menu allows you to define an arbitrary rectangular grid of slip centers above the slope. To add a grid:
Select Add Grid from the toolbar or the Surfaces menu.
You will be prompted to enter the first corner of the grid. Enter the point graphically by clicking with the mouse, or type in x,y coordinates in the prompt line.
As you move the mouse, a rectangular window will be drawn from the first corner to the current cursor location. Enter the second corner of the grid graphically with the mouse, or enter x,y coordinates in the prompt line.
You will see the Grid Spacing dialog. Enter the number of intervals in the X and Y directions. NOTE: the default spacing for a square grid is 20 x 20. For a rectangular grid, the default spacing in the X and Y directions will automatically be calculated, such that the total number of slip centers is approximately 400 (i.e. approximately equivalent to the number of slip centers in a 20 x 20 square grid). Press OK to accept the default values, or enter the desired X and Y grid spacing.
The grid will be added to the model, as illustrated in the Auto Grid topic.
With the Add Grid option, the user can define more than one grid if necessary. Each grid can have different grid spacings. However, note that the Radius Increment will be the same for all grids.
If multiple grids are defined, grids are allowed to overlap or even be entirely within another grid, if for instance you want to define a finer grid over a critical area of a larger grid.
Grids can be created automatically with the Auto Grid option. However, for experienced Slide users, the Add Grid option is recommended, since Auto Grid does not always give suitable results, and it is very simple to manually add a grid using Add Grid.
The display of slip center locations within a grid can be turned on or off in the Display Options dialog.
Grids can be deleted, moved or stretched (re-sized), using the options in the Edit sub-menu in the Surfaces menu, or by using convenient right-click options.