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Strength Criteria
No other slope stability program on the market today gives you the
wide choice of strength models for both soil and rock - most packages
offer a limited set of models that apply only to soils. Slide
not only contains both soil and rock models, it also contains strength
models that allow you to model joint or fault slip and slip along
a geotextile interface. For ultimate flexibility you can also define
the failure criterion yourself.
Select the
method you wish to use.
You can graph the function you have
defined by selecting the Plot button.
For the Generalized Hoek-Brown rock strength
criterion, you can estimate input parameters using convenient built-in
charts and tables of typical values. Just select the"Pick"
button in the Parameter Calculator dialog for the desired parameter
and use the chart or table to determine an appropriate value for the
parameter.
GSI Table for estimating GSI from rock structure
and surface condition.
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Strength Criteria: Discrete Function
The Discrete Function option is a unique new strength model that allows
the user to define the strength at discrete locations within the slope.
Slide then uses interpolation to calculate the strength within
the soil at any point. Often engineers have field strength data or
have calculated strength from a finite-element or other numerical
model. Now Slide can take this data and use it to calculate
the strength at any point within a soil region. All the user needs
do is copy and paste the x,y location and strength values from their
favourite spreadsheet software into Slide.
One method of interpolation that greatly simplifies the modeling of
soil layers that have variable strength according to depth is the
"Linear by Elevation" method. You simply define the strength profile
according to elevation (y-coordinate). You can define either a single
strength value (Cu) or Mohr-Coulomb strengths (c, phi). The strength
at any elevation is then automatically interpolated by a simple linear
interpolation, using the strength data at the defined elevations.
To ensure the correct interpolation of the strength, you can view
the interpolated strength contours in the Intepreter.
Select the Discrete Function strength type.
Paste or type your data into the
spreadsheet.
Select the interpolation method based on
the type of data you have. For example, if your data represents strength
as a function of depth, choose the "Linear by Elevation" interpolation
method.
Results show contours of strength in the
Interpreter and the global minimum failure surface. The strength was
interpolated using 13000 data points generated from a finite-element
model. Notice the complex distribution of strength.
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Strength Criteria: Drained-Undrained Model
The Drained-Undrained strength option allows you to define a soil
strength envelope which considers both drained and undrained Mohr-Coulomb
strength parameters. The shear strength is defined in terms of effective
stress parameters c’ and phi’, up to a maximum value of
shear strength defined by the undrained cohesion Cu.
If you only need to define constant strength parameters which do NOT
vary with depth, then you can enter the parameters directly in the
Define Materials dialog. In this case, the shear strength envelope
is defined by constant values of:
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Cu (undrained cohesion)
c'/Cu ratio (drained
cohesion c' is defined as a fraction of Cu
drained phi' |
Drained-Undrained strength option in Define Materials
dialog.
If the cohesion is variable with depth, then select the "Cohesion
varies with depth" checkbox, and select the Define button. You
will see another dialog in which you can define the undrained and
/ or drained cohesion as a function of depth. The drained cohesion
can be specified as a fraction of the undrained cohesion Cu, or it
can be specified as a function of depth, independently of the undrained
cohesion.
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