fracture contact-model command

Syntax

fracture contact-model keyword <rangeof dfns>

Primary keywords:

activate deactivate distance install model use-aperture

Assign contact models via fractures. The command only applies to PFC. In order for the contact model specified with the model keyword to use the fracture geometry, the contact model must have the property “dip” corresponding to the fracture dip (and “ddir” corresponding to the fracture dip direction, in 3D). The properties assigned to the fractures with the fracture property command are supplied to the contact model. These properties are fixed, in the sense that they will not be inherited from the contacting pieces or previous contacts, and must be specified by the user directly to change their values. Use the contact-model inheritance logic to specify those contact-model properties not specified in the fractures.

It is possible for multiple fractures to intersect a contact. In order to uniquely identify the appropriate contact model, a dominance hierarchy is imposed on the DFNs and fractures. If multiple fractures intersect a contact, the fractures from the DFN with the lowest dominance value are scrutinized. Of these fractures, the fracture with the lowest dominance value is identified as the appropriate fracture for contact model/property assignment. The DFN dominance is specified with the fracture create, fracture generate and fracture import commands.

The list of mechanical contact models is given in the PFC Help, in the Contact Models section. In the documentation for each contact model, a Properties table exists. These include: the linear, linear contact bond, linear parallel bond, hertz, hysteretic, smooth joint, and the flat joint property tables.

activate: Activate contact model assignment when new contacts that intersect a fracture in the specified range are created.

deactivate: Deactivate contact model assignment when new contacts that intersect a fracture in the specified range are created. This applies to all previously activated instances, regardless of the supplied range.

distance f: The distance from the closest point on a fracture to the contact line within which to identify contacts for contact model assignment is set to f. The default value is 0.0. The fracture apertures supersede f if the use-aperture keyword is specified.

install: Install the specified contact model at all existing contacts that intersect a fracture in the range. New contacts that intersect fractures will not be automatically assigned the specified contact model unless the activate keyword is also specified.

model s: Name the contact model to be used (e.g., linear, smoothjoint, etc.).

use-aperture: Use the aperture of each fracture as the distance criteria to identify the contacts for contact model assignment. The apertures supersede the distance provided with the distance keyword.

Usage Example

The following example illustrates how the fracture contact-model command can be used to install the smoothjoint contact model in all contacts intersecting fractures. We first create a cubic assembly of balls and install a default contact model with the contact cmat default command. Then, we generate fractures and assign the properties kn, ks and cohesion to each fracture. The smoothjoint contact model is assigned to each contact intersecting a fracture.

model new
program warning off
model random 10001
model domain extent -5 5
cmat default model linearpbond property kn 1e5 
ball generate cubic
ball attribute density 2500.0 damp 0.7
; create contacts and assign the linearpbond contact model
model clean
fracure generate fracture-count 1000
fracture aperture log-normal 0.1 10 
fracture property 'sj_kn' 1e5 'sj_ks' 1e-4 'sj_coh' 0
; install smoothjoint
fracture contact-model model 'smoothjoint' install use-aperture                     
return 