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| According to the ultrahigh pillar structure and mechanical characteristics, considering the initial geometric deviation caused by mining disturbance, the simplified model of the pressure bar is established. Based on elastic-plastic theory, the deflection and internal forces of ultrahigh pillar with initial geometric imperfections are analyzed and discussed. And based on the Kachanov theory of damage, the damage of ultrahigh pillar is analyzed, the damage failure time is calculated. The results show that under the influence of the initial deflection, pillar will appear different degree of additional deflection, which grows with the increase of initial deflection and pressure ratio. Analysis of engineering examples show that the start time of damage and instability of delay time of pillar has close relationship with initial deflection, pressure ratio and compressive strength. With the increase of pressure ratio and initial deflection, the damage incubation time and the instability of delay time quickly become small, the greater the compressive strength, the greater the instability of the delay time, which means that the pillar is more stable. The results of this study provide a theoretical basis for stability analysis and control of ultrahigh pillar. |
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| Keywords:initial imperfection; ultrahigh pillar; damage creep; instability of delay time; pressure bar |
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