| A large number of mined-out areas usually formed, in the process of mineral resources exploitation,Open-stope method including breasting mining method,room-and-pillar method and shrinkage mining method were adopted in underground mine. While cavity system stability was not dependent on isolated jambs or pointed pillars, but one system including stope roof and floor with jambs or pointed pillars were composed to achieve synergism together. Subordinate mine of KaFang1-9ore body is mainly in Open-stope method to exploit currently. The increasing area of exposure of goaf weakened synergistic effect of Roof-Pillar System or made it dis-synergized with the process of mining owing to irrational schematization and mining technology of continuous stoping in the initial mining stage, which had major potential safety hazard coupling with underground pressure exacerbating of mined-out area partial region. Therefore, relying on engineering practice of1-9ore body mining of Qian Jinkeng KaFang, took Roof-Pillar System of underground mined-out area as research objects, guided by system stability theory. From the research line combined with various ways such as rock mechanics, structural mechanics, system science, catastrophe theory and energy theory etc theoretical research,empirical analysis in addition to numerical modeling approach including synergism concept, which had studied the synergism of Roof-Pillar System following with advance of working face in the process of evolution.(1) Based on fracturing mechanism of roof and pillar, instability mode and mechanism of1-9ore cluster of KaFang thinking of object’s engineering background was discussed. It is well known to us that making a theoretical research and discussion of ordering, dimensionality reduction, entropy decreasing, energy dissipation and release and the catastrophic process of quantitative change to qualitative changes in synergistic effect of mined-out area Roof-Pillar System from the perspective of nonlinear science.(2) The results of theoretical analysis show that the synergic safe thickness of roof with span and collaborative pillar structure were preliminarily analyzed using traditional method of semi-quantitative analysis and safety factor,which based upon the criterion established on the basis of roof and pillar stability.The influencing mechanism of geometric dimensioning property of mined-out area on roof stability and the mechanics response rules of roof in different goaf dimension with FLAC3D were studied by simplified orthogonally test analysis method. Using the3D-σ code, the three-dimensional geologic model of1-9mining area was established, meanwhile, stress field, safety rate etc of system in different scale of stope structure parameter was analyzed. In the long run, the request of synergism of Roof-Pillar System aiming at practical mining at present was considered by improving pillar structure or filling some artificial pillars to perfect internal and external conditions, thus achieving synergy of system.(3) The synergistic mechanical model was established. Based upon the analysis of the sudden and nonlinear of the Roof-Pillar System instability, Cusp Catastrophic Model of synergism was built about system. While the necessary and sufficient conditions of catastrophe instability of Roof-Pillar System were derived and analyzed the stability of system using energy catastrophe, then come to a conclusion that mined-out area system synergism should meet rational stope structure parameter in large scale. The mechanics response rules of Roof-Pillar System under synergistic processing mode in different working conditions was studied, consequently pillars were not arranged in accordance with linear growth in the same recovery ratio. |
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