塌方 is a verb-object compound meaning 'to cave in or collapse', typically used for landslides, cave-ins, or structural collapses of earth or rock. As a separable verb (离合词), the verb 塌 can split from the object 方 when you need to insert time, measure, or aspect markers — for example, 塌了一次方 ('collapsed once'). The object 方 here derives from 地方 ('place, area'), so the literal sense is 'the place collapses', but it's used as a fixed compound for geological or engineering collapses.