Trying to simulate mudpiles or sand drip with particle effect - what should my strategy be?

I'm trying to simulate an effect where a soft structure, like mudpiles or sand drips (see here) accumulates on a plane.

I think there's a way to fake it acceptably through the Unity particle system and its collision properties - if I can find a way to "pile" the particles somehow after they collide with the plane or each other.

Here's an example of what I mean (this is a sand drip): https://www.youtube.com/watch?v=NI95DI1qNmo

This is what I mean by the particle system: https://youtu.be/nKfZBHNeyQo Right now the particles are just overlapping. But if I can find a way for them to somehow stack, I believe I can "fake" adequately the strange combo of liquid + solid that is the hallmark mud piles.

I also think the particle system will be the cheapest performance wise for this (it's a mobile VR concept).

I'm wondering if:

1. I'm on the right track here?

2. Is the solution to create an invisible plane and have it shift up as particles pile up, so the next set of particles "appears" to be stacked on top of the previous one?

3. should I be adding some kind of rigidbody or softbody component to the particles? I worry this will create gaps in the stacking and be expensive.

This is the first question I ask about Unity so please ask for follow-ups in the comments. And I apologize for vagueness.