Control Technology Of Surrounding Rock At Large Section Non-equal Height Intersection

In view of the problems of increasing exposed area and damage scope,complex stress environment and intensified surface deformation at intersection points.Taking the chamber group of belt roadway in the north wing of Gaohe coal mine as the research background,the stress distribution and failure characteristics of surrounding rock at the intersection of non-equal height roadway and the influencing factors are comprehensively analyzed by means of theoretical analysis,numerical simulation and field measurement,and the differential support technology at the intersection of non-equal height intersection is put forward.The main achievements are as follows:(1)The stress distribution law of surrounding rock at intersection point under elastic and elastic-plastic state is analyzed theoretically.It is concluded that the failure range of surrounding rock is positively correlated with roadway radius,buried depth and lateral pressure coefficient,and negatively correlated with surrounding rock strength and intersection angle.The failure characteristics of surrounding rock at the intersection of equal height and non-equal height roadways are compared and analyzed.It is pointed out that the key to control the intersection of non-equal height roadways is to stabilize the roof of branch roadways so as to reduce the equivalent span.(2)The influence of roadway size effect on the stability of surrounding rock at intersection point is analyzed,and the spatial distribution characteristics of stress and deformation characteristics of surrounding rock under different roadway size are revealed.It is pointed out that when the intersection angle is less than 60 degrees,the total deformation of surrounding rock and the range of plastic zone increase sharply.The best arrangement of intersections should be vertical arrangement.(3)The influence law of the variation of branch height on the stability of surrounding rock at the intersection is analyzed and compared in different rock mass structures.This paper puts forward a differential reinforcement scheme.The roof support of roadway side and branch roadway in the coal intersection is strengthened,while the roof support of rock roadway intersection is strengthened.The rib and branch roadway roof need to be strengthened at the coal intersection,while the roof of the main roadway need to be strengthened at the rock intersection.(4)Based on the geological conditions of Gaohe coal mine,the minimum coal pillar width between driving chambers is determined to be 6 m.The roof of the head chamber,the side and the roof of the connecting roadway are strengthened with anchor cables.Field measurements show that the surface displacement of the surrounding rock is small,the roof does not have a separation layer,and the surrounding rock with a depth of more than 2 m is basically free of cracks.The support design meets the stability requirements of the surrounding rock at the intersection.