The Rocscience International Conference 2021 Proceedings are now available. Read Now
 

Search Results

Drained-Undrained Strength

The Drained-Undrained strength option in the Define Material Properties dialog, 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 c’, phi’ and Cu are all constant, then you can simply enter these parameters directly in the Define Material Properties dialog.

If the cohesion is variable with depth:

  1. Select the "Cohesion varies with depth" checkbox in the Define Material Properties dialog.
  2. This will enable the Define button. Select the Define button, and you will see another dialog (the Drained-Undrained Strength Properties dialog), in which you can define the drained and / or undrained cohesion as a function of depth.
  3. By default, the (Undrained) Cohesion Type = F(Depth) and the (Drained) Cohesion Type = F(undrained Cu). However, you may define the Drained and Undrained cohesion using any combination of the options described below.

    Undrained Strength Parameters

    In the Drained-Undrained Strength Properties dialog, the Undrained cohesion can be defined as:

    • Constant
    • F(Depth from Top of Layer)
    • F(Depth from Horizontal Datum)
    • F(Distance to Slope)

    by selecting from the Cohesion Type drop-list.

    Constant

    Cohesion is constant throughout the material.

    F(Depth from Top of Layer)

    Cohesion is a function of depth, where depth is measured from the top of the material layer that is local to the slice, to the center of a slice base.

    • Cu (Top) is the undrained Cohesion at the top of the material layer (local to the slice).
    • Cu Change is the rate of change of undrained Cohesion with depth.
    • If you wish to specify a maximum undrained soil strength, select the Cutoff checkbox and enter a maximum value for Cohesion. If the rate of Cu Change is negative, then the Cutoff value represents the minimum soil strength.
  4. F(Depth from Horizontal Datum)

    Cohesion is a function of depth, where depth is measured from a user specified Datum (y-coordinate) to the center of a slice base.

    • Cu (Datum) is the undrained Cohesion at the Datum elevation.
    • Cu Change is the rate of change of undrained Cohesion with distance (ydatum-y) from the Datum.
    • If you wish to specify a maximum undrained soil strength, select the Cutoff checkbox and enter a maximum value for Cohesion. If the rate of Cu Change is negative, then the Cutoff value represents the minimum soil strength.
    • Datum is the datum elevation (y-coordinate) which is constant elevation for material properties.
  5. F(Distance to Slope)

    Cohesion is a function of depth, where depth is an actual distance measured from closet point on the slope to the center of a slice base.

    • Cu (Slope) is the undrained Cohesion at the top of the slope elevation.
    • Cu Change is the rate of change of undrained Cohesion with depth.
    • If you wish to specify a maximum undrained soil strength, select the Cutoff checkbox and enter a maximum value for Cohesion. If the rate of Cu Change is negative, then the Cutoff value represents the minimum soil strength.
  6. Drained Strength Parameters

    The Drained cohesion can be defined as:

    • Constant
    • F(Depth from Top of Layer)
    • F(Depth from Horizontal Datum)
    • F(Distance to Slope)
    • F(Undrained Cohesion)

    by selecting from the Cohesion Type drop-list.

    Constant

    Cohesion is constant throughout the material.

    F(Depth from Top of Layer)

    Cohesion is a function of depth, where depth is measured from the top of the material layer, to the center of a slice base.

    • c’ (Top) is the drained Cohesion at the top of the material layer (local to the slice).
    • c’ Change is the rate of change of drained Cohesion with depth.
  7. F(Depth from Horizontal Datum)

    Cohesion is a function of depth, where depth is measured from a user specified Datum (y-coordinate) to the center of a slice base.

    • c’ (Datum) is the drained Cohesion at the Datum elevation.
    • c’ Change is the rate of change of drained Cohesion with distance (ydatum-y) from the Datum.
    • Datum is the datum elevation (y-coordinate).
  8. NOTE: a Cutoff value cannot be defined for the Drained cohesion.

    F(Distance to Slope)

    Cohesion is a function of depth, where depth is a vertical distance measured from top of the slope to the center of a slice base.

    • c’ (Slope) is the drained Cohesion at the top of the slope of the model.
    • c’ Change is the rate of change of drained Cohesion with depth.

F(Undrained Cu)

With this option, the drained cohesion c’ is defined as a fraction of the undrained Cu, by entering a c’/Cu ratio. This automatically defines the drained cohesion in terms of the undrained strength. For example, if the undrained cohesion varies with depth, then the drained cohesion will also vary with depth, according to the value of Cu at a given depth, and the c’/Cu ratio.

Friction Angle Phi’

The drained friction angle Phi’ for the material. This parameter does NOT vary with depth.

Note: The drained-undrained material model is a bilinear failure envelope. It uses the minimum of the drained or undrained strength regardless of the water table. For more information on interaction of the strength above water tables please refer to Strength Above Water Surface.


Account Icon - click here to log in or out of your account Shopping Cart icon Click here to search our site Click here to close Learning Tech Support Documentation Info Chevron Delete Back to Top View More" PDF File Calendar Location Language Fees Video Click here to visit Rocscience's LinkedIn page Click here to visit Rocscience's YouTube page Click here to visit Rocscience's Twitter page Click here to visit Rocscience's Facebook page Click here to visit Rocscience's Instagram page Bookmark Network Scroll down for more Checkmark Download Print Back to top Single User Multiple Users CPillar Dips EX3 RocFall RocPlane RocSupport RocTopple RS2 RS3 RSData RSPile Settle3 Slide2 Slide3 SWedge UnWedge Commercial License Education License Trial License Shop safe & secure Money-back guarantee