Morphological characteristics and quantitative discriminant method of superimposed plastic zone expansion of surrounding rock of repeated mining roadway
The problem of surrounding rock failure in repeated mining roadway has always been the central problem of mining discipline research,the key of which lies in the relationship be-tween the morphology of surrounding rock plastic zone before and after the superimposition of two kinds of stresses.In order to study the superposition expansion pattern of the plastic zone of roadway surrounding rock,the superposition expansion law and the mechanism of the plastic zone of different forms were studied by the comprehensive application of numerical sim-ulation experiment and theoretical analysis,and the quantitative discriminant criterion of the superposition plastic zone was proposed,and the discrimination method flow of the superposi-tion plastic zone based on the superposition plastic zone's morphological expansion law and dis-crimination criterion was established.The results show that:1)The superposed plastic zone of roadway surrounding rock can be regarded as the superposition of the morphology of primary plastic zone and secondary plastic zone.When the secondary plastic zone is butterfly shaped,the position expansion of the butterfly leaf is unstable.2)The expansion mechanism of super-position plastic zone is revealed:The pre-state plastic zone generated by primary deviating stress has irreversibility,and the post-state plastic zone generated by superposition secondary stress is a re-failure form based on the damaged surrounding rock,and the post-state plastic zone shape is determined by the magnitude of the deviating stress before and after superposi-tion.The spread deflection position of the superimposed plastic region depends on the deflection angle of the principal stress.3)The quantitative criterion formula and criterion of su-perposed plastic zone of surrounding rock are put forward,and the quantitative criterion of su-perposed plastic zone morphology is put forward through the superposed plastic zone morphol-ogy coefficient.4)The process of quantitative discriminant of superposed plastic zone morphol-ogy is established,and the formation and expansion process of surrounding rock plastic zone before and after repeated mining is perfected through the joint analysis of stope model and plane model,which provides a more accurate theoretical basis for the stability control of sur-rounding rock of repeated mining roadway,and the reliability of this method is verified by en-gineering examples.
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