A pile or the act of piling up; accumulation (noun). Can refer to a physical heap or metaphorical accumulation like records or achievements.
倉庫の資材の積み上げが崩れてけが人が出た。
A stack of materials in the warehouse collapsed and someone was injured.
データの積み上げが多ければ、分析に時間がかかる。
If there's a large accumulation of data, analysis will take longer.
彼は長年の積み上げで信頼を得た。
He earned trust through years of accumulated efforts.