Study on energy characterization and control of unstable coal pillar in dynamic pressure gob-side entry
The failure of coal and rock masses is an instability phenomenon driven by energy,and de-scribing the failure behavior of coal rock from the perspective of energy dissipation is one of the effective methods to evaluate the stability and safety of engineering operation.Based on the finite difference me-thod for energy dissipation,it is proposed that the failure position and degree of coal rock can be charac-terized by high-concentration energy dissipation regions and the density of energy dissipation,respective-ly.Accordingly,the post-peak strain softening and deformation failure behavior of coal rock can be elu-cidated.In this study,by simplifying the coal pillar in gob-side entry under dynamic pressure into a plane strain model,the evolution law of dissipated energy of coal pillars during overburden deformation was investigated,and the deformation and instability paths of coal pillars were revealed from the per-spective of energy.The results demonstrate that energy dissipation of coal pillars mainly occurs in the post-peak and residual stages.The post-peak shear plane is connected with the corner energy dissipation region,and it shifts inward with the increase of loading degree.Once the elastic zone disappears,the coal pillar is prone to instability.The energy dissipation and stability of a coal pillar are related to its width,loading degree,and loading mode.Furthermore,an active support model of coal pillars was es-tablished,and the control effect of bolt(cable)support on energy dissipation was explored.It was found that bolt(cable)support can effectively improve the transfer and distribution of dissipated energy,and that an increase in support strength is conducive to enhancing the ductility and deformation resistance of coal pillars.Besides,different support patterns exert a control effect on energy dissipation to varying de-grees.Specifically,the control effect of cable support is better than that of bolt support,and bidirectional grouting cable support is superior to conventional cable support.Finally,by taking narrow coal pillars in a retained roadway in Yushuling Coal Mine as an example,the field application of"an-chor and bidirectional grouting cable"support on narrow coal pillars was introduced,which brought about a remarkable control effect.
gob-side entrychain pillardeformation and failureevolution of energystability control
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