Research on Mechanical Properties of Narrow Coal Pillars Based on Lateral Confinement Compression Test

Aiming at the stability of narrow coal pillar under the condition of gob-side entry driving, the mechanical properties of coal pillar under different boundary conditions and stress are studied through pressure tests. The results are as follows: after simplifying the multi-axis stress state of narrow coal pillar to the lateral confinement problem, the compressive test under the lateral confinement condition is “CC” type: σ₁> σ₂> 0; through the compressive tests under multiple confined conditions, the properties of narrow coal pillar in the confined conditions were obtained: compressive strength under double-sided lateral confining conditions > uniaxial compressive strength, its lateral strength coefficient K is between 1.2 to 1.85; double-sided lateral elastic modulus < elastic modulus of uniaxial compression; residual strain point ε_pm of double-sided confined compression test > uniaxial compression test ε_pn.