Damage Evolution Characteristics and Constitutive Model for Coal and Rock under Asymmetric Loading

Area of Science:

• Geotechnical Engineering
• Rock Mechanics
• Mining Engineering

Background:

• Underground excavations like tunnels and roadways experience asymmetric loading from geological conditions and excavation processes.
• Understanding the mechanical response and failure mechanisms of coal rock under such conditions is crucial for safety and stability.

Purpose of the Study:

• To investigate the influence of varying degrees of asymmetric loading on the mechanical properties and failure laws of coal rock.
• To analyze the macro- and micromechanical effects of asymmetric loading coefficients.
• To develop a statistical damage constitutive model for coal and rock under asymmetric loading.

Main Methods:

• Conducted uniaxial compression tests on coal rock specimens under four distinct asymmetric loading modes.
• Analyzed the impact of asymmetric coefficients on macro- and micromechanical behaviors.
• Developed and utilized a statistical damage constitutive model to simulate asymmetric loading effects.

Main Results:

• Peak stress in coal rock decreases linearly with increasing asymmetric loading coefficient.
• Acoustic emission ringing count peak distribution shifts from concentrated (uniform loading) to scattered multiphase (asymmetric loading).
• Asymmetric loading induces stress concentration, leading to shear failure and crack localization near loading zone interfaces.

Conclusions:

• Asymmetric loading significantly alters the mechanical properties and failure characteristics of coal rock.
• The established constitutive model demonstrates that higher asymmetric coefficients correlate with reduced strain at equivalent damage levels.
• Asymmetric loading demonstrably promotes damage accumulation in coal and rock, posing risks to underground structure integrity.