Shear Wave Loading of a Model with Free-Field Boundaries (FLAC2D)

Verification Problem

The project file for this example may be viewed/run in FLAC2D.[1] The main data file used is shown at the end of this example.

How To Read and Use Examples

A simple example of the use of the free-field boundary condition is presented. Figure 1 shows the final model geometry.

../../../../../_images/freefield-geometry1.png

Figure 1: Side and corner free-field boundaries in a FLAC3D model.

A shear stress wave is applied to the base of the model. Figure 2 shows the resulting \(x\)-velocity at the top of the model at different points in both the free field and the main grid.

../../../../../_images/freefield-xvel.png

Figure 2: x-velocity histories at top of model with free-field boundaries, at four different locations in the main grid and the free-field zones.

Data File

ShearWaveFreeFieldBoundModel.dat

;---------------------------------------------------------------------
;              Script file for Dynamic Problem
;              Shear wave loading of a model with free-field boundaries
;---------------------------------------------------------------------
model new
model large-strain off
fish automatic-create off
model title "Shear wave loading of a model mech with free-field boundaries"
model configure dynamic
;
; Create zones
zone create quadrilateral size 6 2
zone create quadrilateral size 2 2 point 0 (0,2)
zone create quadrilateral size 2 2 point 0 (4,2)
zone create triangle size 1 2 point 0 (2,2)
zone create triangle size 1 2 point 0 (3,2) point 1 (4,2) point 2 (4,4)
;
; Name model boundaries
zone face skin
;
; Assign model and properties
zone cmodel assign elastic
zone property bulk 66667 shear 40000 density 0.0025
;
; Set Initial Conditions
model gravity 10
zone initialize-stresses ratio 0.25
;
; Set Boundary Conditions - Roller boundaries
zone face apply velocity-normal 0 range group 'West2' or 'East2' or 'Bottom'
;
; Static equilibrium
model dynamic active off
model solve convergence 1
model save 'FreeFieldInit'
;
; --- dynamic run A: applied velocity at base ---
zone face apply-remove range group 'Bottom'  ; Remove velocity boundary
zone face apply quiet range group 'Bottom' ; Add quiet boundary
fish define wave
    wave = 0.5 * (1.0 - math.cos(math.pi*zone.dynamic.time.total*200.0))
end
zone face apply stress-xy -1.0 fish wave range group 'Bottom' 
                               ; Time varying stress boundary
zone dynamic free-field on     ; Free field boundaries
; Histories
model history name='time' dynamic time-total
zone history name='grid'   velocity-x position (2,4.0)
zone history name='ff' velocity-x position (-1.4,4.0)

;
; Solve to time 0.015
model dynamic active on
model solve time-total 0.015
model save 'FreeField'

Endnote