Abstract: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≤0.45,the gateway surrounding rock is in stable state and while C>0.45,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.