Shear Wave On Stiff Wall In Soft Soil: Dynamic Multi-Stepping (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

This small and simple example illustrates the effect of dynamic multi-stepping. The model consists of a “wall” of material with a modulus 150 times greater than the surrounding material. A shear wave is applied at the base of the model for a 1 s time period.

With zone dynamic multi-step on, 20 zones have a multiplier of 1, and 580 zones have a multiplier of 8. The calculation is three times faster with dynamic multi-stepping on a 6-core CPU. The \(x\)-velocity histories monitored at the base of the model and top of the wall are identical with and without multi-stepping. Figure 1 plots the histories for the multi-stepping run.

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Figure 1: x-velocities at model base and top of wall.

Data File

ShearWaveOnStiffWallInSoftSoil.dat

;---------------------------------------------------------------------
;              Dynamic Example 
;              Shear wave applied to a stiff wall in a soft soil
;              With dymanic multistep
;---------------------------------------------------------------------
model new skip fish table
model large-strain off
model title ...
      'Shear wave applied to a stiff wall in a soft soil with dyn. multistep'
model configure dynamic
;
; Create zones
zone create quadrilateral size 40 20 ...
                  point 0 (-5,0) point 1 (15,0) ...
                  point 2 (-5,10)
zone face skin ; Label model boundaries
;
; Assign model and properties
zone cmodel assign elastic
zone null range position-x=-5,5 position-y=5,10
zone property young 20e4 poisson 0.2 density 2000
zone property young 30e6 range position-x=5,6 position-y=5,10
;
; Boundary conditions
zone face apply velocity-y 0 range group 'East' or 'West'
fish define wave
    wave = math.sin(math.pi * dynamic.time.total / 16.0)
end
zone face apply velocity-x = 1 fish [wave] range group 'Bottom'
zone face apply velocity-normal 0          range group 'Bottom'
;
; Histories
zone history name='xvelb' velocity-x position (5,0)
zone history name='xvelt' velocity-x position (5,10)
zone history name='zvelt' velocity-y position (5,10)
model history name='time' dynamic time-total
;
; Set multi-step status, and cycle to 32, timing how long that takes
zone dynamic multi-step [multi]
[global start = time.clock] 
model solve time-total 32.0
[global time = (time.clock - start)/100]
[time]

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