FLAC3D Theory and Background • Zone Joints

Creation of Zone Joint Geometry

Zone Joints are created with the zone joint create command. Zones must first be separated using the zone separate command, unless two separate sub-grids exist that do not share nodes and faces. Zone joints can only be created between separate faces and nodes - not in the middle of contiguous zones.

Unlike interfaces, zone joints are two-sided. They are made by first creating walls on the opposing faces. Contacts then form automatically between the walls. So, the procedure for creating zone joints is similar to creating interfaces, with the following extra considerations:

  • Before creating zone joints, you need to issue the command zone joint configure. This sets up the required data structures for zone joints, turns the model to small strain (large strain is not currently supported with zone joints), and sets the default contact model to the Mohr model.

  • Before creating zone joints you need to separate all of the faces. This is different from interfaces where the separation and interface creation can be done simultaneously. Since zone joints are two-sided, this approach will not work since all of the intersections need to be resolved before creating the zone joints.

  • Faces on both sides of the separation must be identified. The easiest ways to do this are to group the internal faces before separation, or skin the model after separation (zone skin). Note that meshes imported from Griddle already have group names assigned to the internal faces.

A simple example illustrating the procedure for zone joint creation is provided in “DippingJoint.dat”. The corresponding project file, “DippingJoint.prj”, is located in the folder “FLAC\ZoneJoint\DippingJoint”. The same example is also provided in 2D. The example is a block specimen containing a single joint dipping at an angle of 45°.


model new

zone create brick size 3 3 3 ...
        point 0 (0,0,0) point 1 (3,0,0) point 2 (0,3,0) point 3 (0,0,1.5) ...
        point 4 (3,3,0) point 5 (0,3,1.5) point 6 (3,0,4.5) point 7 (3,3,4.5) ...
        group 'Base'
zone create brick size 3 3 3 ...
        point 0 (0,0,1.5) point 1 (3,0,4.5) point 2 (0,3,1.5) point 3 (0,0,6) ...
        point 4 (3,3,4.5) point 5 (0,3,6) point 6 (3,0,6) point 7 (3,3,6) ...
        group 'Top'

; Create zone joints

; first assign group name to faces to be separated
zone face group 'Joint' internal range group 'Top' group 'Base'

; now separate
zone separate by-face range group 'Joint'

; now create zone joints
zone joint configure 
zone joint create by-face range group 'Joint'

Figure 1 shows the zones. Two sub-grid groups are defined: a Base grid and a Top grid. Figure 2 shows the model with the zone joints between the zones.


Figure 1: Initial geometry before creation of the zone joint.


Figure 2: Zone Joint.