Underhand Closed Bench Mining for Seismic Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Deep narrow vein mining methods, such as cut and fill and longhole mining, often result in high ground stresses leading to mining-induced seismic events, posing safety risks and damage to excavations, especially at depths exceeding 3,000 feet where seismic vibrations can cause tunnel collapse and disrupt production.
Innovation Solution
The underhand closed bench technique involves drilling large diameter blast holes vertically into the vein from the floor of the excavation, using emulsion explosives to proactively trigger seismic events on faults at predetermined times, directing stress waves into the rock mass and fragmenting ore laterally and upward, thereby controlling seismic activity and ensuring safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional cut and fill or longhole mining methods are used, then ore extraction can proceed, but high ground stresses concentrate in pillars between mined voids, causing mining-induced seismic events that damage excavations and threaten personnel safety
Solution Approach 1:
The patent inverts the traditional mining sequence by mining from the top down rather than bottom up. Horizontal cuts are advanced at the top of the ore body, and material is removed downward through vertical shafts. This inversion eliminates the need for支撑 pillars between mined voids, as each cut is immediately backfilled, thereby eliminating the concentration of ground stresses that cause seismic events while maintaining continuous ore extraction productivity
Solution Approach 2:
The patent applies preliminary action by backfilling each horizontal cut immediately after ore removal, before proceeding to the next cut below. This immediate backfilling stabilizes the rock mass and prevents stress concentration from developing, proactively preventing seismic events before they can occur during subsequent mining operations
2Productivity
If vertical advance on multiple mining levels is implemented to create sufficient production, then ore extraction capacity increases, but ground stresses become concentrated in pillars trapped between mined voids, resulting in seismic events and tunnel collapse
Solution Approach 1:
By inverting the mining sequence to top-down operation, the patent eliminates the creation of multiple mined voids at different levels that would require supporting pillars. Each horizontal cut is mined and immediately backfilled, creating a continuous, stable rock mass that eliminates stress concentration zones and prevents tunnel collapse, thereby maintaining both high production capacity and excavation stability
Solution Approach 2:
The patent applies beforehand cushioning by immediately backfilling each mined cut with waste material from the mill before proceeding to the next level. This backfill acts as a cushion that absorbs and distributes ground stresses, preventing their concentration in pillars and eliminating the risk of seismic events and tunnel collapse while enabling continuous multi-level production
3Ease of manufacture
If conventional blasting methods are used, then ore is fragmented for recovery, but seismic vibrations from blasting can cause tunnel collapse and are dangerous to mining personnel
Solution Approach 1:
The patent applies preliminary action by conducting blasting operations in horizontally advanced cuts that are immediately backfilled after ore removal. This timing ensures that any seismic vibrations from blasting occur in already-stabilized rock mass with backfill in place, preventing tunnel collapse and protecting personnel while still achieving effective ore fragmentation for recovery
Solution Approach 2:
By inverting the mining sequence to mine from the top down with immediate backfilling, the patent positions blasting operations within stabilized, backfilled cavities rather than in open voids. This inversion ensures that blasting-induced seismic vibrations are contained and absorbed by the backfill and surrounding rock mass, eliminating the danger of tunnel collapse while maintaining ore fragmentation effectiveness
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This technique enhances safety by scheduling seismic events when personnel are not present, reduces damage to excavations, and increases production and predictability compared to standard methods, while providing a stable work environment with engineered roofs.
Implementation Method 1
directing stress waves into the rock mass and fragmenting ore laterally and upward
Implementation Method 2
using emulsion explosives to proactively trigger seismic events on faults at predetermined times
Data Source
AI summary
The present invention relates to systems and methods of mining, including drilling a first plurality of blast holes along a length of a horizontal stope and blasting explosive within the first plurality of blast holes. The method includes recovering fragmented ore from the horizontal stope and stabilizing the horizontal stope via a first engineered roof. The method then includes drilling a second plurality of blast holes along the length of the horizontal stope and blasting explosive within the second plurality of blast holes. The method further includes recovering fragmented ore from the horizontal stope and stabilizing the horizontal stope via a second engineered roof. The horizontal stope is mined in a downward direction.