Software: PFC: Pre-Release 4.0
Smooth Joint Contact Model
The joint geometry of a single smooth-joint contact is defined by a plane that is comprised of two initially coincident planar surfaces. The two contacting particles are permanently associated with the two surfaces, one per side. The contact force-displacement law provides Coulomb sliding with dilation. During each time step, the relative displacement increment between the ball surfaces is decomposed into components normal and tangential to the joint surfaces. These components are multiplied by the shear and normal joint stiffnesses to produce increments of joint force.
standard contact model (relative normal and tangential displacements with respect to the contact orientation)
smooth joint model (relative normal and tangential displacements with respect to the joint orientation)
The joint is described as "smooth" because particles that have been assigned a smooth-joint contact may overlap. This insures that the particles will "slide" as expected along the joint, rather than be forced to move around one another.
motion of upper particle with an ordinary contact when subjected to a lateral force
motion of upper particle with a smooth-joint contact when subjected to a lateral force
Frictional joints may be modeled as collections of smooth-joint contacts.
The images above show a PFC2D and PFC3D model with a single, through-going frictional joint. At left the specimens are shown with the initial definition of the joint in blue. The smooth-joint contacts are shown in red. The specimens are subjected to uniaxial compression as part of an unconfined-compression test. The velocity fields for both models, shown at right, indicate that the specimens fail by sliding along the joint.
 |
 |
Replay |
Replay |
Full Version [wmv: 3.14Mb] |
Full Version [wmv: 2.49Mb] |
The images above show PFC2D (left) and PFC3D (right) specimens that contain a through-going joint with friction coefficient of zero. The bottom layer of particles is fixed, a wall is placed at left to stop the motion of the upper block, and gravity acts downward. Note that as displacements occur new smooth-joint contacts are created between particles that have come into contact as a result of large shearing motion.
For a complete, detailed technical specification of the smooth joint contact model, please see the document "Smooth Joint" [1.54Mb].
LOP Slope shows a practical application that uses the smooth-joint contact model.
