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Tension Cracks
A tension crack zone can be defined in Slide by adding
a tension crack boundary, above which a tension crack zone will
exist. The boundary is a simple polyline which is added by typing
in the coordinates and/or interactively using the mouse to enter
the points. The region above the tension crack boundary, and within
the external boundary, will then be shaded with a vertical line
pattern, to highlight the tension crack zone you have created (ie.
a tension crack boundary defines the lower limit of a tension crack
zone).
During the analysis, any slip surface which intersects the tension
crack boundary is extended vertically upwards until it intersects
the ground surface. A further driving force due to water
in the tension crack can be included in the analysis by using
one of several different methods for defining the water level in
the tension crack.
Tension crack zone (vertical line fill in yellow soil
region).
Surfaces intersecting a tension crack zone. Notice how
they are extended vertically upwards at the point of intersection
with the tension crack boundary.
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Tension Cracks: Water Level in Tension Crack Zones
The water level in a tension crack zone is very important to the stability analysis, because the additional hydrostatic force which can be exerted by water in a tension crack, can significantly lower the factor of safety of slip surfaces which intersect the tension crack zone.
There are several different options for defining the water level in a Tension Crack.
| Dry |
A completely dry Tension Crack zone. No additional hydrostatic forces will act on the slip surface. |
| Filled |
A completely water-filled Tension Crack zone. This is the worst case scenario, and will exert the maximum hydrostatic force on the slip surface. |
| Percent Filled |
A percentage from 0 to 100 can be specified. This percentage defines the height of water in the Tension Crack, along any vertical line from the Tension Crack boundary to the ground surface. |
| Filled Below Elevation |
This option allows the user to enter a value of Elevation, defining the water level in the Tension Crack zone. |
| Filled to Depth |
This option allows the user to enter a value of Depth. This defines the level of water in the Tension Crack zone, relative to the position of the Tension Crack boundary. |
| Use Water Table / Use Piezometric Line |
If your model includes a Water Table or Piezometric Lines, then the water level in the Tension Crack zone can be automatically defined by the location of the Water Table, or a Piezometric Line. The Tension Crack zone will be assumed to be full of water, between the Tension Crack boundary, and the Water Table or Piezometric Line, if the Water Table or Piezometric Line is drawn through the Tension Crack zone. |
Dialog for specifying how the water level in a tension crack is defined
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