Failure Evolution and Instability Mechanism of Surrounding Rock for Close-Distance Parallel Chambers with Super-Large Section in Deep Coal Mines

Acknowledgments

Notation

c

cohesion of rock;

E₁

microelement at the center of two parallel chambers;

E₂

microelement in the elastic-plastic junction of Chamber 1;

E₃

microelement between the two parallel chambers;

E₄

microelement in the elastic-plastic junction of Chamber 2;

L₁

spacing between E₁ and two chambers;

L₂

critical chamber spacing without chain instability;

R

chamber radius;

R_P

radius of the plastic circle;

R*

loosening circle radius;

$R_P^{*}$

new plastic circle radius;

R*^a

critical radius of loosening circle without chain instability;

P₀

original rock stress;

S₁

moving distance when Chamber 2 reached Chamber 1 elastic-plastic junction;

S₂

moving distance of loosening circle;

S₃

moving distance of loosening circle when E reaches E₄;

σ_a

stress generated by Chamber 2 in E₂;

σ_b

original stress in E₂;

${\sigma }_c^Z$

superimposed stress of Chambers 1 and 2 in the elastic-plastic junction of Chamber 1;

σ_d

stress generated by Chamber 1* in E₄;

σ_e

original stress in E₄;

σ_f

superimposed stress of Chambers 1* and 2;

${\sigma }_f^Z$

superimposed stress of Chambers 1 and 2 in the elastic-plastic junction of Chamber 2;

σ_θ1

maximum stress of Chamber 1 in the elastic-plastic junction;

σ_θ2

maximum stress of Chamber 2 in the elastic-plastic junction;

${\sigma }_r^{*}$

radial stress in the loose circle;

${\sigma }_{\theta }^{*}$

tangential stress in the loose circle;

${\sigma }_T^{*}$

residual strength of the rock mass in the loosening circle;

φ

friction angle of element A; and

μ*

Poisson’s ratio of rock mass in the loosening circle.

References