basic question concerning the oedemeter test code

Asked by Rioual on 2019-03-18

Hello,

I am testing the oedometer test program (see below) and I have a few basic questions of understanding:

1- "while 1:" (see *****1*****): what is exactly the condition "1" ?? what does this instruction mean ??

2- How do you control exactly the order of the different processes:
A-making the packing first by making the particles grow
B- then "oedemeter section, check bulk modulus
C- then starting oedemeter simulation
with O.run(200,1) (on last line) you are supposed to read all the script before the line 200 times so redo the
 previous processes (A and B) ?? which you don't want.

Thank you for your enlightements,

Fr.

# -*- coding: utf-8 -*-
#*************************************************************************
# Copyright (C) 2010 by Bruno Chareyre *
# bruno.chareyre_at_grenoble-inp.fr *
# *
# This program is free software; it is licensed under the terms of the *
# GNU General Public License v2 or later. See file LICENSE for details. *
#*************************************************************************/

## Example script for using the DEM-PFV coupling introduced with E. Catalano, as reported in:
## * [Chareyre2012a] Chareyre, B., Cortis, A., Catalano, E., Barthélemy, E. (2012), Pore-scale modeling of viscous flow and induced forces in dense sphere packings. Transport in Porous Media (92), pages 473-493. DOI 10.1007/s11242-011-9915-6
## http://dx.doi.org/10.1007/s11242-011-9915-6
## * [Catalano2014a] Catalano, E., Chareyre, B., Barthélémy, E. (2013), Pore-scale modeling of fluid-particles interaction and emerging poromechanical effects. International Journal for Numerical and Analytical Methods in Geomechanics. DOI 10.1002/nag.2198
## http://arxiv.org/pdf/1304.4895.pdf
## Also used in:
## * Tong et al.2012 (http://dx.doi.org/10.2516/ogst/2012032)
## * Sari et al 2011 (http://people.3sr-grenoble.fr/users/bchareyre/pubs/SariChareyreCatalanoPhilippeVincens_Particles2011.pdf)

## The DEM-PFV is applied here to 1D consolidation (oedometer test). The example includes the determination of oedometer modulus Ee and permeability K.
## The 1D consolidation is simulated as a coupled problem and the analytical solution corresponding to the abovementionned Ee and K is used for comparison.
## See triax-tutorial/script-session1.py for more detailed explanations of the packing generation procedure.

## ______________ First section, similar to triax-tutorial/script-session1.py _________________
from yade import pack

num_spheres=1000# number of spheres
young=1e6
compFricDegree = 3 # initial contact friction during the confining phase
finalFricDegree = 30 # contact friction during the deviatoric loading
mn,mx=Vector3(0,0,0),Vector3(1,1,1) # corners of the initial packing

O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=radians(compFricDegree),density=2600,label='spheres'))
O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=0,density=0,label='walls'))
walls=aabbWalls([mn,mx],thickness=0,material='walls')
wallIds=O.bodies.append(walls)

sp=pack.SpherePack()
sp.makeCloud(mn,mx,-1,0.3333,num_spheres,False, 0.95,seed=1) #"seed" make the "random" generation always the same
sp.toSimulation(material='spheres')

triax=TriaxialStressController(
 maxMultiplier=1.+2e4/young, # spheres growing factor (fast growth)
 finalMaxMultiplier=1.+2e3/young, # spheres growing factor (slow growth)
 thickness = 0,
 stressMask = 7,
 max_vel = 0.005,
 internalCompaction=True, # If true the confining pressure is generated by growing particles
)

newton=NewtonIntegrator(damping=0.2)

O.engines=[
 ForceResetter(),
 InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb()]),
 InteractionLoop(
  [Ig2_Sphere_Sphere_ScGeom(),Ig2_Box_Sphere_ScGeom()],
  [Ip2_FrictMat_FrictMat_FrictPhys()],
  [Law2_ScGeom_FrictPhys_CundallStrack()],label="iloop"
 ),
 FlowEngine(dead=1,label="flow"),#introduced as a dead engine for the moment, see 2nd section
 GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8),
 triax,
 newton
]

triax.goal1=triax.goal2=triax.goal3=-10000

while 1: (******1******)
  O.run(1000, True)
  unb=unbalancedForce()
  if unb<0.001 and abs(-10000-triax.meanStress)/10000<0.001:
    break

setContactFriction(radians(finalFricDegree))

## ______________ Oedometer section _________________

#A. Check bulk modulus of the dry material from load/unload cycles
triax.stressMask=2
triax.goal1=triax.goal3=0

triax.internalCompaction=False
triax.wall_bottom_activated=False
#load
triax.goal2=-11000; O.run(2000,1)
#unload
triax.goal2=-10000; O.run(2000,1)
#load
triax.goal2=-11000; O.run(2000,1)
e22=triax.strain[1]
#unload
triax.goal2=-10000; O.run(2000,1)

e22=e22-triax.strain[1]
modulus = 1000./abs(e22)

#B. Activate flow engine and set boundary conditions in order to get permeability
flow.dead=0
flow.defTolerance=0.3
flow.meshUpdateInterval=200
flow.useSolver=3
flow.permeabilityFactor=1
flow.viscosity=10
flow.bndCondIsPressure=[0,0,1,1,0,0]
flow.bndCondValue=[0,0,1,0,0,0]
flow.boundaryUseMaxMin=[0,0,0,0,0,0]
O.dt=0.1e-3
O.dynDt=False

O.run(1,1)
Qin = flow.getBoundaryFlux(2)
Qout = flow.getBoundaryFlux(3)
permeability = abs(Qin)/1.e-4 #size is one, we compute K=V/∇H
print "Qin=",Qin," Qout=",Qout," permeability=",permeability

#C. now the oedometer test, drained at the top, impermeable at the bottom plate
flow.bndCondIsPressure=[0,0,0,1,0,0]
flow.bndCondValue=[0,0,0,0,0,0]
flow.updateTriangulation=True #force remeshing to reflect new BC immediately
newton.damping=0

#we want the theoretical value from Terzaghi's solution
#keep in mind that we are not in an homogeneous material and the small strain
#assumption is not verified => we don't expect perfect match
#there can be also an overshoot of pressure in the very beginning due to dynamic effects
Cv=permeability*modulus/1e4
zeroTime=O.time
zeroe22 = - triax.strain[1]
dryFraction=0.05 #the top layer is affected by drainage on a certain depth, we account for it here
drye22 = 1000/modulus*dryFraction
wetHeight=1*(1-dryFraction)

def consolidation(Tv): #see your soil mechanics handbook...
 U=1
 for k in range(50):
  M=pi/2*(2*k+1)
  U=U-2/M**2*exp(-M**2*Tv)
 return U

triax.goal2=-11000

from yade import plot

## a function saving variables
def history():
   plot.addData(e22=-triax.strain[1]-zeroe22,e22_theory=drye22+(1-dryFraction)*consolidation((O.time-zeroTime)*Cv/wetHeight**2)*1000./modulus,t=O.time,p=flow.getPorePressure((0.5,0.1,0.5)),s22=-triax.stress(3)[1]-10000)
   #plot.addData(e22=-triax.strain[1],t=O.time,s22=-triax.stress(2)[1],p=flow.MeasurePorePressure((0.5,0.5,0.5)))

O.engines=O.engines+[PyRunner(iterPeriod=200,command='history()',label='recorder')]
##make nice animations:
#O.engines=O.engines+[PyRunner(iterPeriod=200,command='flow.saveVtk()')]

from yade import plot
plot.plots={'t':('e22','e22_theory',None,'s22','p')}
plot.plot()
O.saveTmp()
O.timingEnabled=1
from yade import timing
print "starting oedometer simulation"
O.run(200,1)
timing.stats()

Question information

Language:
English Edit question
Status:
Solved
For:
Yade Edit question
Assignee:
No assignee Edit question
Solved by:
Robert Caulk
Solved:
2019-03-19
Last query:
2019-03-19
Last reply:
2019-03-18
Best Robert Caulk (rcaulk) said : #1

Hello,

>>1- "while 1:" (see *****1*****): what is exactly the condition "1" ?? what does this instruction mean

1 is equivalent to "True" for logic statements in Python. That while loop will run until "break" is called.

>>2- How do you control exactly the order of the different processes:

I think the Yade tutorial will help you understand Yade syntax and the methods for how Yade scripts work [1]. Every time you call "O.run(xxx)" you are telling Yade to cycle through the engine list you've created, xxx times. Any code between O.run(xxx) calls is simply modifying the scene to start and stop the different processes. I guess the exact code for how to control the processes is outlined in #A, #B, #C.

Cheers,

Robert

[1]https://yade-dev.gitlab.io/trunk/tutorial-geo.html

Rioual (francois-rioual-v) said : #2

Thanks Robert Caulk, that solved my question.