Hi there,
I’m trying to model an excavation in clay using FLAC2D. The stratigraphy goes as follow, 27m of clay, purple zones, laying on the bedrock, green zone. Here is my mesh:
Gravity is taken to be 9.81m/s2, units are m, Mg, kPa and s and boundary conditions are:
fix x (sides)
fix x y (bottom)
The strategy is to use the Mohr-Coulomb Model to evaluate displacement resulting from the unloading of the clay (excavation). The rock is modelled as an elastic medium. Material properties are :
model mohr group ‘Clay’
prop density=1.3 bulk=8300 shear=3800 group ‘Clay’
prop cohesion=13.5 friction=31.0 group ‘Clay’
model elastic group ‘Rock’
prop density=2.3 bulk=6.7E4 shear=4E4 group ‘Rock’
I established effective stresses and pore pressures using a FISH function called Ininv.fis and solved mechanical only.
set flow off
water density 1
;
; Call Fish functions
call ‘Ininv.fis’
set cd back
set wth=17 k0x=1 k0z=1
ininv
;
; Solve
history 999 unbalanced
solve
The equilibrium is reached with minimal displacements. Vertical displacement reached 0.4 m total which seems normal for a 272m high model. I then initialize velocities and displacement and proceed to excavate the clay using model null on zones to be excavated.
initial xdisp 0 ydisp 0
initial xvel 0 yvel 0
set flow off
water bulk 0
model null i=215,250 j=133,148
history 999 unbal
solve
The solution converges but the zones atop of the slope start to strain very weirdly. Anybody can help?
