What are the main requirements of good timbers used in mining?

The main requirements for good timbers used in mining focus on their structural integrity and functionality rather than aesthetics or cost. Proper length, straight grain, and adequate sizing are crucial because these characteristics ensure that the timber can effectively support the weight of the surrounding materials, resist breakage under pressure, and provide stability to mine structures.

Timbers that are of proper length ensure that they fit correctly within the mine's framework, while a straight grain indicates that the wood has uniform strength properties, reducing the risk of failure during use. Adequate sizing refers to the thickness and width of the timber, which must be sufficient to carry the loads it will encounter without bending or breaking. These requirements help maintain safety in mining operations, preventing accidents that could arise from inadequate structural support.

A focus on the physical attributes of timber enhances both durability and safety in a hazardous environment, which is the primary concern in mining operations, making this answer the most appropriate choice.