Gravity Settlement in a Coupled PFC-FLAC3D model

Problem Statement

Note

To view this project in the program, use the menu command Help ► Examples…. Choose “—————/ ————–” and select “——-.—- to load. The main data file used is shown at the end of this example. The remaining data files can be found in the project.

The following example illustrates gravity settlement in a vertical column using PFC-FLAC3D coupling. The bar is composed of particles bonded together on the top part of the system, and of zones on the bottom part. The bottom end is a fixed boundary. The PFC and FLAC3D regions overlap over a specified length, where they are coupled using the Ball-Zone coupling scheme. Gravity is activated and the system is solved to equilibrium.

The behavior of the coupled system is compared with a similar system composed of balls alone (PFC-only model), and a system composed of zones alone (FLAC3D-only model). The three systems are run side-by-side in the same model.

Numerical Model

The data file “settle_cpl.dat” simulates gravity settlement in a column made up of a coupled PFC-FLAC3D system. The vertical displacement at the top of the system is shown in

Figure 1: Displacement histories.

Figure 2: Displacement contours.

Data File

settle_cpl.dat

model new
model configure dynamic
model large-strain on

[rho    = 2700.0 ]
[emod   = 75.0e9 ]
[nu     = 0.25]
[mmod   = emod*(1-nu)/((1+nu)*(1-2.0*nu))]

[l  = 1.0]
[nb = 5]

[rad  = l/(2.0*nb)]
[rhob = 6.0/math.pi*rho]

[nh   =  10]
[nw   =  1]
[npfc =  2]
[ncpl =  3]
[h    = nh*l]
[nf3d =  nh - (npfc+ncpl)]

;[lsub  = nzh*hz]
[hmin  = 0.]
[hpfc = hmin +  nf3d      *l]
[hf3d = hmin + (nf3d+ncpl)*l]
[nf = int(hf3d/l)]

[epsilon = 1.0e-3]

zone create brick size  [nw] [nw] [nf]  point 0 0   0   [hmin] ...
                                        point 1 [l] 0   [hmin] ...
                                        point 2 0   [l] [hmin] ...
                                        point 3 0   0   [hf3d]

zone create brick size  [nw] [nw] [nh]  point 0  [2.0*l] 0.  [hmin] ...
                                        point 1  [3.0*l] 0.  [hmin] ...
                                        point 2  [2.0*l] [l] [hmin] ...
                                        point 3  [2.0*l] 0.  [h]
zone cmodel assign elastic
zone property young [emod] poisson [nu]
zone initialize density [rho]
model cycle 0 ; to initialize gp masses

model range create 'bottom' position-z [hmin-0.01*l] [hmin+0.01*l]
zone face group 'bottom' range named-range 'bottom'
zone gridpoint fix velocity range named-range 'bottom'
zone gridpoint fix velocity-x
zone gridpoint fix velocity-y

;
model domain extent [-4.0*l] [4.0*l] [-2.0*l] ...
                    [2.0*l] [hmin-5.0*rad] [h+5.0*rad]
ball generate cubic radius [rad] box [rad] [l-rad] [rad] ...
                                     [l-rad]  [hpfc+rad] [h-rad]

ball generate cubic radius [rad] box [-2.0*l+rad] [-l-rad] [rad] ...
                                     [l-rad]  [hmin+rad] [h-rad]
ball fix velocity range position-z [hmin] [hmin+2.0*rad]
ball fix velocity-x velocity-y

ball attribute density [rhob]
contact cmat default model linearpbond ...
                     method pb_deformability emod [4.0/math.pi*mmod] ...
                     kratio 1.0 ...
                     property pb_ten 1e20 pb_coh 1e20

model clean
contact method bond gap 0.01

model gravity (0,0,-9.81)
zone dynamic damping local 0.1
zone mechanical damping local 0.1
ball attribute damp 0.1

ball-zone create

fish define setMassFactors(eps)
  loop foreach local cb ball.zone.ball.list
    local b = ball.zone.ball.ball(cb)
    local bzpos = ball.pos.z(b)
    ball.extra(b,1) = (1.0-2.0*eps)*(hpfc - bzpos)/(hpfc-hf3d) + eps
    ball.zone.ball.mass.factor(cb) = ball.extra(b,1)
  endloop
  loop foreach local cgp ball.zone.gp.list
    local gp     = ball.zone.gp.gp(cgp)
    local gpzpos = gp.pos.z(gp)
    gp.extra(gp,1) = (1.0-2.0*eps)*(hf3d - gpzpos)/(hf3d - hpfc) + eps
    ball.zone.gp.mass.factor(cgp) = gp.extra(gp,1)
  endloop
end
[setMassFactors(epsilon)]

history interval 1
model history name '1' mechanical time-total
model history name '2' mechanical ratio-average
zone history name '11' displacement-z position ([2.0*l],0.0,[h])
ball history name '12' displacement-z position (0.0,0.0,[h])
ball history name '14' displacement-z position ([-2.0*l],0.0,[h])

zone history name '21' displacement-z position ([2.0*l],0.0,[hpfc])
ball history name '22' displacement-z position (0.0,0.0,[hpfc])
zone history name '23' displacement-z position (0.0,0.0,[hpfc])
ball history name '24' displacement-z position ([-2.0*l],0.0,[hpfc])

zone history name '31' displacement-z position ([2.0*l],0.0,[hf3d])
ball history name '32' displacement-z position (0.0,0.0,[hf3d])
zone history name '33' displacement-z position (0.0,0.0,[hf3d])
ball history name '34' displacement-z position ([-2.0*l],0.0,[hf3d])

model save 'settle_cpl-ini'
model solve ratio-average 5e-3
model save 'settle_cpl-final'
program return