深部开采的定量界定与分析

Quantitative definition and investigation of deep mining

随着我国煤炭开采深度不断增加,"深部开采"将成为常态,但是什么是"深部",如何定义"深部",始终没有科学的、定量化的表达。提出了亚临界深度、临界深度、超临界深度等概念和定义,用于表征不同程度的深部开采。经研究"深部"不是深度,而是一种力学状态,是由地应力水平、采动应力状态和围岩属性共同决定的力学状态,可以通过力学分析给出定量化表征。研究表明,随着采深增大,原岩应力趋于静水应力状态是深部的1个典型和共同的特征,同时煤岩体也经历了弹性变形破坏、脆塑性转变和大范围屈服等阶段。深部开采中极高的地应力水平和三向等压应力状态将导致深部围岩大范围塑性破坏并伴随大量级、大规模的强烈动力失稳,现有的煤炭开采理论与技术已难以适用,需要对深部岩体力学、采矿科学理论进行新探索。

With the continuous increase of coal mining depth in China,‘deep mining'is becoming a common practice. However,the terminology ‘deep mining'has not been scientifically and quantitatively defined. This paper proposes the definitions of subcritical depth,critical depth,and supercritical depth in an attempt to characterize deep mining in various degrees. It is stated that‘deep mining'should not be simply related to the depth of mining activities below ground surface,but rather to the stress condition determined by in-situ stresses,mining-induced stresses and the geological and geotechnical conditions of rock masses. A quantitative characterization of‘deep mining'can be given by investigating the stress conditions. The results from this study show that as mining depth increases,in-situ stress trends to approaching hydrostatic state,along with the transition from elastic-deformation failure,plastic-deformation failure to massive failure in rock masses. Under deep mining conditions,a high hydrostatic pressure can result in a massive plastic failure of rock masses,companying with high magnitude,large-scale dynamic instability.The theories and technologies used in normal mining activities are not applicable to deep mining conditions. This necessitates systematic investigation on the rock mechanics and theories in deep mining.