近风氧化带开采导水裂隙发育规律及机制分析

 为寻求提高开采上限导高发育规律，以40例“两带”探测钻孔实测数据为依据，应用回归分析方法对3种水体采动等级下不同覆岩类型的导水裂隙高度进行非线性统计研究，并首次建立3类水体下的预留防水煤岩柱与裂采比间的BoxLucas1模型曲线。研究发现：提高开采上限时，BoxLuca1曲线预测导水高度的误差值远小于常规“三下”规程经验公式误差，表明该模型的合理性；3类水体的曲线斜率逐渐增大，顺序为II，III类＞I类，表明II，III类裂采比下降更快，导高发育受到风氧化带的抑制作用更加明显。而且I，II类水体下的导水裂隙顶界面未达到泥化层的底界面，III类水体下的裂隙未达到或未穿透风氧化带。说明在一定范围内提高开采上限是可行的。在此基础上，一方面利用Paris位移公式和Crouch不连续位移公式，提出风氧化带拉张型裂隙面的位移公式，计算结果表明，该带裂隙受上覆自重应力影响更容易因发生变形位移和刚度位移而产生弥合效应。另一方面，风氧化带特有的塑性大变形使得外力对该带所做的功大部分被其消耗掉，因而更容易损耗劈裂能量，从而抑制导水裂隙的继续向上发育。这可为该带下合理留设防水煤岩柱提高煤层开采上限提供理论依据。

ANALYSIS OF DEVELOPING MECHANISM OF WATER TRANSMITTING FRACTURED ZONE MINING APPROACHING TO WEATHERED AND OXIDIZED ZONE

Nonlinear statistical analysis of heights of zones with water transmitting fractures at three different grades of underwater mining beneath various roof rocks was conducted with the regression method and the measured data of 40 drillings. A BoxLucas1 curve between the ratio of heights of fractured to mining zones and the height of waterproof coal pillar was established，which produced smaller errors than the conventional empirical formula did. The slopes of curves for 3 types of water gradually increased and the values of types II and III were greater than that of type I，which indicated that the height of water transmitted fractured zone under water mining type I was more easily reduced by the inhibition effect of weathered and oxidized zone. The fracture of type III did not penetrate the weathered and oxidized zone as mining closing to this area and the top interfaces of water transmitted fractures of types I and II did not reach the bottom of the mud layer，which indicated that raising the upper limit of mining within a certain range was feasible. A displacement formula for tensile fracture surfaces of weathered and oxidized zone was proposed utilizing Paris?s formula of displacement and Crouch?s formula of discontinuous displacement. The calculated results show that the fractures are more easily closed due to the overlying gravity. The large plastic deformation of weathered and oxidized zone consumes the work by external forces and consumes splitting energy easily，which prevents water transmitted fractures from upward development.