Hi everyone,

I’m trying to simulate liquefaction using PM4Sand in FLAC8.1. For now, I only simulate the ground (no structure), and I use a sinusoidal wave as the input motion.

The pore pressure increases as expected, but the Yacc (acceleration) seems to drop too early, which is not what I expected. I already attached the input wave image.

I have tried:

Changing the damping ratio

Also tried running without damping

But the results are the same.

Now I’m wondering if the problem is in my static condition. Here are the steps I used for static part:

Solve the model with elastic settings (Mohr-Coulomb model)

Set flow on to include the water level

Then I use mech on, and continue to dynamic simulation

My questions:

Are these steps correct for a good static condition before doing dyn? If not, what is the correct order? Or, is there something missing about pm4sand properties I used ?

And also, For ru calculation, I saved the effective stress just before dyn, after initial static stage. Then I calculated ru using those values. Is this method okay for create RU curve ?

I also attached the code I used for all the steps.

Thank you so much. I really hope someone can help me 🙏