What is primarily used to prevent the earth from collapsing into a closed well?

The primary purpose of casing in a closed well is to prevent the walls of the well from collapsing. Casing refers to the tubular structure installed in the well to maintain well integrity and provide stability to its structure. This is especially important in areas with loose soil or other unstable ground materials, where the weight and pressure can lead to the collapse of the well walls if not properly supported.

Casing also protects the well from contamination by surface water and external substances, ensuring the quality of the water within the well. While other materials such as rock, concrete, or steel pipes may be involved in well construction, they serve different roles. For example, rock may provide a natural barrier in certain geological conditions, and concrete can be used in various forms for structural purposes. However, casing is specifically designed to line the well and directly prevent collapse, making it the most suitable choice for this function.