Jointed Material

The effects of strength anisotropy due to jointing or other planes of weakness can be accounted for with the Jointed Material option. Using a "ubiquitous joints" approach (Azami et.al. 2012 , Zinkewiecz & Pande 1977), you may define 1, 2 or 3 distinct joint orientations each with its own strength criterion. To define a jointed material:

1. In the Define Material Properties dialog select the Jointed Material check box in the Strength Parameters section.

NOTE: the Jointed Material option is only available in conjunction with the Mohr-Coulomb or Generalized Hoek-Brown Failure Criterion.

2. Select the Joint Options button and you will see the Joint Options dialog.
3. In the Joint Options dialog you can define 1, 2 or 3 distinct joint orientations each with its own slip criterion. For each joint:
4. Enter the joint Inclination (with respect to the X-axis, counter-clockwise positive) or use the Trace Plane option (see below for details).
• For details on the strength models see the Define Joint Properties topic.
5. When you are finished defining the joint properties select [OK].

During the analysis, RS2 will simultaneously consider:

• the joint strength (defined by the joint slip criterion)
• the rock mass strength (defined by the rock mass Failure Criterion)

at the gauss point(s) of each finite element. Failure may then occur in the rock mass and/or along joint plane(s) at each gauss point.

Joint Orientation

There are two methods of defining the Joint Orientation - Inclination or Trace Plane.

Inclination

The Inclination is the angle of the joint plane as measured from the X-axis of the model. Values can range between -90 degrees and 90 degrees.

Use Trace Plane

The Trace Plane as defined in the Joint Options dialog is simply the cross-sectional plane of your RS2 model. It is assumed that the Trace Plane is vertical (i.e. your RS2 model is horizontal).

If the Use Trace Plane option is selected, then you can enter the 3-dimensional Dip and Dip Direction of a joint, and the Trace Plane orientation, and RS2 will automatically determine the 2-dimensional projection of the joint on the trace plane. If you are using this option, it is important to note the following:

• The Trace Plane is assumed to be vertical (i.e. Dip = 90 degrees). Therefore only the Trace Plane Dip Direction is required. This is the direction (i.e. trend or azimuth) of the normal vector of the Trace Plane, measured clockwise from north. Also note, the normal vector is assumed to be pointing INTO the screen (i.e. away from the viewer).
• The Dip and Dip Direction of the joint plane follows the standard definition, although only positive values are allowed. The joint plane cannot be exactly parallel to the trace plane.

Remember that the RS2 plane strain analysis is 2-dimensional. When you enter the 3-dimensional joint plane orientations, you are NOT defining a 3-dimensional joint network. RS2 only uses the 3-dimensional information, to determine the 2-dimensional traces of the joint planes on the trace plane. Once this has been determined, the actual analysis is 2-dimensional (i.e. the model will behave as if the joints were perpendicular to the trace plane).

Joint Slip Criterion

See the Define Joint Properties topic for definitions of the Joint Slip Criterion parameters.

NOTE:

• do not confuse the Jointed Material option in the RS2 Model program, with the Ubiquitous Joints option in the RS2 Interpret program. The Jointed Material option is used during the stress analysis, and failure along joints will affect stresses and displacements in the rock mass. The Ubiquitous Joints option in Interpret is a post-analysis feature used only for computing strength factor, but does not affect the calculated stresses or displacements.
• there are other methods of explicitly modeling jointed rock masses in RS2, using joint boundaries or joint networks, see the Joints Overview topic for more information.