采动覆岩裂隙体系统耗散结构特征与突变失稳阈值效应

Dissipative structure feature of mining fractured overburden system and threshold effect of catastrophic instability

将覆岩裂隙体作为系统来考虑,分析了采动覆岩裂隙体系统动态演化过程中的耗散结构特征,采用分形维数描述了采动裂隙发育过程及系统演化、涨落与跃迁;引入"孔隙压力熵"研究了采动覆岩裂隙体系统耗散结构演化中的熵变过程,并在近平衡态广义力与广义流的基础上明确了远离平衡态非线性区的超广义力及其驱动的广义流,依据超熵临界判据分析了以开采尺度为指标的动力失稳阈值。结果表明:可以通过耗散结构理论描述覆岩裂隙化程度与采空空间之间关系;孔隙压力熵可以描述采动覆岩裂隙体系统在由自然状态向采动状态逐步演化的"熵减"现象;孔隙压力熵的二次变分随开采尺度演化曲线的斜率为系统在远离平衡态非线性区的超熵产生,并以此为指标可判断系统在外界约束条件变化下的3种演化趋势,揭示了系统隔水性能在临界开采尺度下的失稳阈值效应。

The fracture overburden was considered as a system, and the dissipative structure characteristics during the dynamic evolution of mining overburden fracture system have been analyzed. Fractal dimension of mining fractures in the overburden has been used to describe the evolution of the fracture, fluctuation and transition of the system. The "pore pressure entropy" has then been introduced to study the entropy change in dissipative structures of mining fractured overburden system. Based on the asymptotic-equilibrium generalized force and generalized flow, the super-generalized force and the generalized flow driven by it which is far from the equilibrium non-linear region, have been defined. The dynamic instability threshold with mining scale as the index has been analyzed according to the super-entropy critical criterion. The results have shown that the relationship between fracturing degree of overburden and goaf space can be escribed by dissipative structure theory, and the possible range of "huge fluctuation" can be predicted. In addition, Pore pressure entropy can be used for describing the "entropy reduction" in the evolution from natural state to mining state in mining overburden fracture system. The quadratic variation of pore pressure entropy, taking slope of the curve of mining scale generation as system, can be generated with super-entropy which is far from equilibrium state in the non-linear zone, and it is used as an index to determine the three system evolution trends under external constraints. And the threshold effect of system instability of the waterproof performance is revealed at critical mining scale.