to be piled up in an immense heap like a mountain, describing a physical accumulation

irrefutable evidence

military orders are as immovable as mountains and must be strictly obeyed without question

A defeated army collapsing like a landslide; used as an idiom to describe a total rout or sudden, irreversible failure.

to maintain the law as firm as a mountain; to enforce the law strictly

a military order or command that is fixed, unchangeable, and must be strictly obeyed

sickness comes like a landslide, but goes slowly like spinning silk; expect to convalesce slowly