Dynamic evolution of bed separation volume and strata migration in coal seam groups under repeated mining

Area of Science:

• Mining Engineering
• Geotechnical Engineering
• Rock Mechanics

Background:

• Coal seam groups under ultra-thick sandstone aquifers present significant mining safety challenges.
• Understanding strata behavior and bed-separation evolution is critical for safe mining operations.

Purpose of the Study:

• To investigate the geological conditions and bed-separation evolution in the Yanjiahe Mine.
• To analyze the impact of different mining methods on strata behavior and safety.

Main Methods:

• Physical simulation of upward and downward mining in multiple coal seams.
• Numerical modeling to simulate strata migration patterns.
• In-situ monitoring using borehole peeping to observe overlying strata evolution.

Main Results:

• Bed-separation volume evolves through Fracture Type (FT), Cavity Type (CT), and Cavity+Fracture Type (CFT).
• Strata migration follows a Lower Type (LT) → Higher Type (HT) → Lower Type (LT) pattern.
• Observed evolution of bed-separation in overlying strata includes Lower Fracture Type (LFT) to Higher Fracture Type (HFT) and back to LFT.

Conclusions:

• Mining methods significantly influence the expansion characteristics and migration patterns of bed-separation spaces.
• The study provides crucial insights into strata behavior for enhancing safety in complex mining environments.
• Findings contribute to developing effective strategies for managing risks associated with coal seam group mining.