Translation guide
Describes things accumulating in a heap or stack, or tasks/work building up. Japanese uses different verbs depending on what is piling up and whether the focus is on the physical heap or the accumulation of intangible things.
Describe books, dishes, laundry, snow, etc. forming a pile.
Used when objects are deliberately stacked or piled up by someone. Transitive verb 積む (to pile up) in passive/resultative form.
A lot of books are piled up on the desk.
Used for things that accumulate naturally, like snow, dust, or leaves. Intransitive verb 積もる (to pile up, accumulate).
Snow is piled up as high as one meter.
Literally 'become a mountain pile'. Emphasizes a large, often disorderly heap. Common for laundry, dishes, paperwork.
The laundry is piled up in a mountain.
Focuses on things being stacked on top of each other, often neatly. Intransitive verb 重なる (to overlap, be piled up).
Papers are piled up on the desk.
Describe emails, homework, stress, etc. building up over time.
General term for things accumulating, often with a negative nuance of being overdue or needing attention. Used for work, stress, emails.
Work has piled up and I have no time to rest.
Emphasizes gradual accumulation layer by layer, often used for experience, achievements, or problems.
積もる is for physical things that form a heap (snow, dust). 溜まる is for things that accumulate in a container or abstractly (water, work, stress). Using 溜まる for snow would sound odd.
Snow is piled up.
Work is piled up.
English 'be piled up' often translates to different Japanese verbs depending on what is piling up. Direct translation like パイルされている is not natural Japanese.
Small mistakes piled up and became a big problem.