崩れる and 崩す: walls, disrupted schedules, and breaking a bill
Compare 崩れる for a wall or schedule changing with 崩す for knocking down a tower or breaking a bill, preserving both physical and additional meanings.
崩れる applies to a stone wall and a schedule
「大雨で石垣の一部が崩れた。」 says that part of a stone wall collapsed in heavy rain. 石垣の一部 identifies what changed, and 崩れた describes that part collapsing.
「一人が欠席しただけで、作業の予定が崩れてしまった。」 applies 崩れる to a disrupted work schedule. Its English translation is “One person's absence disrupted the entire work schedule.” Preserve entire in this translation without importing an all-schedules or all-work claim into the Japanese or Korean wording.
崩す can knock down a tower or break a bill
「子どもが積み木の塔を手で崩した。」 says that a child knocked down a tower of blocks by hand. 子ども identifies the actor, 積み木の塔 the object, and 手で the use of the child's hand.
「千円札を崩すために小さな品を買った。」 describes buying a small item to get change for a 1,000-yen bill. 千円札を崩す means breaking the bill into change, rather than destroying it. ために states the purchase's purpose; the purchase alone does not confirm that change was received.
Follow the object to the appropriate meaning
The wall and schedule examples use 崩れる for a change affecting the named object. The tower and bill examples use 崩す for acting on an object. For the tower, the action is knocking it down; for the bill, it is exchanging it for smaller denominations.
作業の予定が崩れる figuratively describes a schedule falling apart, while 千円札を崩す means breaking a bill. Read these alongside the physical wall and tower examples. No item price or amount of change received is supplied.
What changes in 作業の予定が崩れる, what does 千円札を崩す mean, and does buying the item confirm receipt of change?
Show the answer and why
The work schedule becomes disrupted, while the bill expression means breaking a 1,000-yen bill into change. 崩れる also describes part of a wall collapsing, and 崩す can describe knocking down a block tower. The purchase is presented as a means to obtain change, so receipt of change is not confirmed.