Why is horizontal development often done before vertical development?

Solution (By Examveda Team)

Horizontal development, such as driving tunnels into a hillside, often precedes vertical development (sinking shafts) because it provides crucial access to the orebody. Tunnels allow for easier and safer transportation of equipment, personnel, and mined materials.

Furthermore, horizontal development enables early establishment of drainage systems. Water accumulation in underground mines can be a major safety and operational hazard. Establishing drainage channels and sumps horizontally allows for more controlled and effective water management before extensive vertical workings are created, preventing water from rushing down shafts and flooding deeper levels.

Why other options are incorrect:

Option A: Easier blasting: While blasting might be simpler in some horizontal situations, it's not the primary reason for prioritizing horizontal over vertical development. Blasting techniques are adaptable to both horizontal and vertical environments.

Option B: Faster machinery deployment: Machinery deployment is facilitated by access, which is a consequence of horizontal development, but not the main driving factor in the sequencing decision.

Option D: Lower equipment cost: Equipment costs can vary based on the specific mining method and geological conditions, but aren't fundamentally different between horizontal and vertical development to a significant enough degree to justify the choice. The costs are often comparable, and access provided by horizontal developments often allows for safer, more efficient equipment use, indirectly lowering overall costs in the long run.