小煤矿复采煤柱塑性区特征及采准巷道支护技术

CHARACTERISTICS OF PLASTIC ZONE OF SECOND MINING PILLAR AND SUPPORT TECHNOLOGY OF GATEWAY IN SMALL MINES

平顶山新华区为全国重点采煤县(区),区内小煤矿井田位于平顶山煤业集团所属矿井浅部报废水平内,主要开采大型矿井开采后遗留煤柱。煤柱受力状态可简化为平面应力状态,受两侧长壁工作面采动影响,煤柱塑性区宽度较大,其主要影响因素是煤层厚度、煤层硬度、煤层与顶底板岩层界面的粘结性能、煤层埋深。当煤层硬度一定时,随着煤层与顶底板界面粘结性能的提高,煤柱塑性区宽度增长的速度递减;当煤层顶底板粘结性能一定时,随煤层埋深的增加,煤柱塑性区宽度增加。大量的现场观测研究表明,在一定支护条件下,巷道围岩稳定性和变形特性与围岩应力和围岩岩性关系,是围岩应力与围岩岩性相互作用的结果,可以引用围岩有效载荷系数C来进行解释。当C≤0.45时,巷道围岩处于稳定状态;当C>0.45时,巷道围岩开始出现流变。当前新华区小煤矿采深通常为200～400 m,不同硬度的煤层采准巷道围岩有效载荷系数相对较小,围岩处于稳定或较稳定状态,所以在目前条件下,新华区小煤矿采准巷道采用刚性木棚支护是较合理的。

The small mines in Xinhua District of Pingdingshan City, Henan Province, one of the China National Key Coal Production Counties (or Districts ), is generally situated in the shallow abandoned mining levels of the large mine of Pingdingshan Coal Group of China. The small mines are mainly mining retained pillars that the large mines left. The pillar stress state can be simplified to plane stress state. Under the mining activities of long wall coalfaces at two sides, the width of plastic zone of pillar is big. Its main influential factors are coal seam thickness, coal seam hardness, bond properties of the interfaces between coal seam and its roof-floor stratum, and the coal seam buried depth. While the coal seam hardness is definite, the increasing velocity of the width of the plastic zone of pillar decrease with the increase of interfacial bond property between coal seam and roof. While the interfacial bond property is unchanged, the width of plastic zone of pillar increases with the increase of buried depth of coal seam. While the type of gateway support is fixed, the stability and deformation characteristics of gateway surrounding rock are related to its stress and property of surrounding rock, and they are the result of interaction between them. Therefore, the effective load coefficient C of surrounding rock can be used to study the stability and deformation characteristics of gateway surrounding rock. When C&le0.45, the gateway surrounding rock is in stable state and while C&le0.45, rheologic deformation begins to occur. At present, since the mining depth of small mines in Xinhua District is about 200-400 m, and the value of effective load coefficient of gateway surrounding rock is relatively small, the gateway surrounding rock is in a stable or relatively stable state. Therefore, from the practical point of view, the rigid timber supports employed in the gateways of small mines in Xinhua District are reasonable.