Physical simulation and theoretical evolution for ground fissures triggered by underground coal mining.

Area of Science:

• Geotechnical Engineering
• Mining Engineering
• Rock Mechanics

Background:

• Underground coal mining causes geological strata movement, subsidence, and ground fissures.
• Previous lab tests focused mainly on fissure formation behind the working panel.

Purpose of the Study:

• To investigate the mechanisms of ground fissure generation and propagation in overlying strata.
• To analyze stress distribution and crack initiation in roof strata during mining panel advancement.

Main Methods:

• Two physical simulation tests with improved strata material properties and artificial pressure devices.
• Development and application of a "cantilever beam and elastic foundation beam" mechanical model.

Main Results:

• Maximum internal forces in roof strata consistently occurred in front of the working panel.
• Roof strata breakage predominantly happened above the gob due to stress concentration from bending and rotation.
• Crack initiation and propagation directions were influenced by internal forces, overburden separation, and hydraulic shield positions.

Conclusions:

• Ground fissures in roof strata are primarily caused by stress concentration above the gob, not solely behind the working panel.
• The dynamic nature of the mining process leads to variable crack initiation points and propagation patterns.
• Understanding these mechanisms is crucial for mitigating mining-induced ground fissures.