Summary of Error Codes

When a safety factor cannot be calculated for a slip surface, Slide will write an error code to the output file, rather than a safety factor. These error codes are NEGATIVE numbers such as –101, -102, -103 etc.

These error codes are displayed when you are using the Query Invalid Surfaces option, the Filter Surfaces option, and they are also listed in the Info Viewer analysis summary.

TIP: the most convenient way to view slip surfaces which correspond to error codes, is to use the Filter Surfaces option, select the Surfaces with Error Code option in the dialog, and select the error code. This will display the surfaces on the model corresponding to the error code, and may help you to troubleshoot or understand why the error code is occurring.

The meaning of these error codes is summarized below.




Circular slip surface is entirely within the tension crack zone.


Slip surface intersects an infinite strength material. If infinite strength materials are defined for a model, a large number of potential slip surfaces may show this error code. This is normal.


(This error code not currently in use. Formerly it was a check for both slip surface / slope intersections having the same y-coordinate e.g. intersection with a horizontal surface. However, this screened out valid surfaces in some cases, and is no longer in use).


Only one (or none) slip surface / slope intersections.


Two slip circle / slope intersections, but resulting arc is actually outside soil region (i.e. the slip circle is tangent to the slope at two locations).


Two slip surface / slope intersections, but one or more slip surface / nonslope External Boundary intersections lie between them. This usually occurs when a slip circle extends past the bottom of the External Boundary, but may also occur on a benched slope model, when a double set of Slope Limits is being used.


Same as –102, but slip circle / nonslope intersections also exist. These points lie outside the arc defined by the two slip circle / slope intersections.


More than two slip surface / slope intersections with no valid slip surface.


Average slice width is less than .0001 * (maximum horizontal extent of soil region). This can occur if a slip surface only intersects a very small portion of the slope, or when a nearly vertical slip surface is created. This limitation is imposed to avoid numerical errors which may result from too many slices, or too small a slip region.


Total driving moment (Bishop) or total driving force (Janbu) is negative. This will occur if the wrong failure direction is specified, or if high loads are applied against the expected slip direction (e.g. distributed, line or anchor loads).


The absolute value of the total driving moment or total driving force is < 0.1. This is to limit the calculation of extremely high safety factors if the driving force is very small. (0.1 is an arbitrary number). This most often occurs when a slip surface intersects a horizontal portion of the slope (driving force or moment can be zero, or a very small number).


Soiltype for slice base not located. This error should occur only rarely. It may occur for circular slip surfaces, if a low number of slices is combined with certain soil geometries, such that the midpoint of a slice base is actually outside the External Boundary, even though the circular slip surface is wholly within the External Boundary.


The water table or a piezoline does not span the slip region for a given slip surface, when Water Surfaces is specified as the method of pore pressure calculation in Project Settings. If this error occurs, check that the water table or piezoline(s) span all the appropriate material zones.


Safety factor iteration did not converge within the Maximum Number of Iterations specified in the Analysis Methods dialog (normal convergence is within 3 or 4 iterations for Bishop / Janbu analysis methods). If this occurs, very low safety factors, or incorrect material properties may be the cause.


The coefficient ma = cosa(1 + tanatanf / F) < 0.2 for the final iteration of the safety factor calculation. This screens out some slip surfaces which may not be valid in the context of the analysis, in particular, deep seated slip surfaces with many high negative base angle slices in the passive zone.

NOTE: if you wish to calculate a safety factor for these surfaces, you can clear the checkbox for the "Check m_alpha < 0.2" option in Project Settings in the Slide Model program, before you run the analysis. See the Analysis Methods topic for details.


Slip surface intersects the External Boundary outside of user defined Slope Limits. This only applies if a slip surface does not intersect the slope within user defined Slope Limits, but does intersect within the default Slope Limits. If a slip surface does not intersect within the default Slope Limits, then error code –101 will apply.


Slip surface has reverse curvature. This can occur when the slip center of a circular slip surface is below the upper y-coordinates of the slope. If you wish to analyze such surfaces, make sure that the Create Tension Crack For Reverse Curvature Surfaces option is selected in the Surface Options dialog.


Surface is too shallow. Maximum height of any slice is LESS THAN the Minimum depth value, specified in the Surface Options dialog. This error code will only be reported if the Minimum Depth option has been enabled in the Surface Options dialog.


Not enough slices to analyze the surface. This may occur if the number of intersections of the slip surface with material boundaries, is greater than the Number of Slices specified in Project Settings. This may occur if you have a large number of material boundaries and / or a low number of slices. To avoid this error code, increase the Number of Slices in Project Settings.


Error in Discrete Interpolation of strength parameters. Either the discrete function was not found or the interpolation did not work.


Surface does not pass through the Search Focus.


Non-circular slip surface is entirely within the tension crack zone.


Tensile effective normal stress on the base of a slice exceeds the tensile strength of the material. This check is only applied if the Tensile Stress Check option is selected in Project Settings > Methods > Advanced.

Allowable tensile stress is zero for all strength criteria models, except: Hoek-Brown, Generalized Hoek-Brown and Shear-Normal strength function. For these 3 models, a tensile strength can exist. See the Analysis Methods topic for more information.


Factor of safety = 0. Possibly due to normal / shear resistance = zero along part of the slip surface.


Cannot generate interslice force function.

In addition to these codes for individual slip surfaces, the output file will list -1000 instead of a minimum safety factor at a slip center grid point (CIRCULAR analysis only), as described below.


Only used if no valid slip circles are generated at a grid center. This will typically occur if a slip center grid is too far over to one side of a model, so that all circles at a grid center only intersect the slope at one location (error code -101 (see above) will probably account for most of the invalid slip circles).