I am trying to simulate the effect of the installation of PVDs on soft soil (soil model used: MCC). The installation of PVD (in this case, a line drain) causes disturbance to the soil and creates three zones around the soil. A smear zone, a transition zone and an undisturbed zone. The horizontal coefficient of permeability is constant in the smear zone, linearly increasing in the transition zone and constant in the undisturbed zone. How can we input this varying permeability in the horizontal direction? And when I plot the excess pore pressure with respect to the horizontal distance, the excess pore pressure is not zero at the drain boundary. How can I make it zero?
Dear Akhil,
Well, in short: there is no possibility in PLAXIS to have a linear variation in permeability within a material set. You could model it as stepwise change with multiple material sets, but that is the closest you will get.
The excess pore pressures at the drain should be zero. So I don't know how you plotted it, but be aware that for instance results in cross sections and shaded plots are the results of interpolation and smoothening stress point values. So this may be the cause that you see values that are not zero.
With kind regards,
Dennis Waterman
After the calculation phase, I took a line cross-section starting from the line drain (0,0,-1.5) where 1.5 is the depth of the soil to (0,1,-1.5). This is how I plotted excess pore pressure vs horizontal distance.This is the result I got.
Like I mentioned, with a cross section quite some data handling is going on (because a cross section never passes exactly through the stress points and/or nodes) and therefore results may not be so accurate.A finer mesh or making sure that the cross section runs exactly over an existing geometry line may improve that.