What is the term used for the action of excessive weight causing a roof to sag?

The correct term for the action of excessive weight causing a roof to sag is referred to as "creep." Creep specifically describes the gradual movement or deformation of material under sustained load or stress over time, which can lead to a sagging effect in structures like mine roofs. This phenomenon occurs when the materials cannot withstand the weight, causing them to yield or deform, often resulting in a slow but continuous downward movement.

In the context of mining, understanding creep is crucial for assessing roof stability and predicting potential hazards associated with unsupported or overly loaded areas. It is distinct from sudden failures but emphasizes the need for preventive measures to ensure safety in underground operations. The other terms, while related to structural issues, do not accurately describe the specific gradual process of sagging due to excessive weight.