From Longman Dictionary of Contemporary Englishpile up phrasal verb1 INCREASE IN ACTIVITY, FEELINGS ETCto increase in quantity or amount, in a way that is difficult to manage It wasn’t long before the debts were piling up. The traffic starts piling up around this time. The work has a tendency to pile up if I’m not careful.2 pile something ↔ up to arrange things in a pile tiny doughnuts piled up in a dish → pileup → pile→ See Verb table
Examples from the Corpus
pile up• The work just keeps on piling up and makes me want to scream.• As her debts piled up, she came close to a nervous breakdown. 