What is the term for the caved-in area after pillars are removed in coal mining?

The term for the caved-in area after pillars are removed in coal mining is "gob." This refers to the void or the area where material has collapsed, often resulting from the removal of supporting structures, such as pillars. In the context of coal mining, maintaining the integrity of mine structures while extracting coal is crucial, and the gob represents an area where coal has been extracted, leading to the collapse of the surrounding rock or soil.

Understanding this term is fundamental in coal mining operations, as it helps mining engineers and workers assess the stability of the mine and manage the safety of the mining environment. The other terms listed, while relevant to aspects of mining, do not specifically describe the caved-in area that occurs as a direct consequence of pillar removal.