Failure Mode And Control Technology Of Surrounding Rock In Mining Roadway With Composite Roof In Nanshan Coal Mine

Surrounding rock control of roadway with composite roof is always a hot and difficult point in roadway support research.Most of the mining roadways are excavated in the coal seam,mostly characterized by composite roofs,and closed to the disturbance source,which lead to a large number of roadway surrounding rock deformation,serious support failure,roof fall accidents occur from time to time.Aiming at the problems such as the serious deformation of surrounding rock at roadway sides and roof fall in roadway with composite roof,comprehensive research methods including theoretical analysis,numerical simulation and field detection were adopted to study the fracture form and deformation law of surrounding rock of mining roadway,analyze the stress environment characteristics of mining roadway,obtain the influence law of rock mass structure and stress environment such as strength,position and thickness of each layer of roadway roof on the expansion and distribution of plastic zone partition of surrounding rock,and clarify the internal correlation between the expansion and distribution characteristics of the plastic zone barriers and the roof fall height and roof fall shape of the roadway with composite roof in Nanshan Coal Mine mining roadway.Based on this,a roof control method based on the fracture morphological characteristics of the composite roof and a high-extensibility composite bolt slab deformation control technology based on the large deformation of the roadway slab are proposed,which provide a certain degree for the control of the surrounding rock of the composite roof mining roadway in Nanshan Mine.The technical support also provided useful supplements for the plastic zone distribution of the surrounding rock of this type of roadway,the failure mechanism of the surrounding rock,and the surrounding rock control technology.The main achievements of this paper are as follows:(1)The failure law of surrounding rock of mining roadway with composite roof is mastered,and the roof fall mechanism of mining roadway with composite roof is revealed.The internal cause of roof fall is that the plastic zone of weak interlayer in the deep roof penetrates through the distribution,resulting in the fracture and failure of hard rock below;the external cause is that the bolt(cable)is broken or the anchor fails to prevent the self-weight collapse of broken rock.(2)A mechanical model of the stability of the roadway with weak interlayer roof is established.Introducing the stress intensity factor to explore the internal relationship between the distribution of the weak interlayer fracture zone,the supporting force and the stability of the underlying hard rock layer,that is,the overall fracture pattern of the roadway roof mainly depends on the thickness of the weak interlayer,the failure state and the physical mechanics of the underlying hard rock layer Based on this,a control method based on the rupture of the composite roof is proposed.(3)A high-extensibility combined bolt is developed.This bolt has sufficient extensibility and shear resistance to ensure the large deformation conditions of the ledge.The lower anchor rod does not break and can continue to provide high support resistance,which can restrain the large deformation and damage of the roadway ledge to the greatest extent,and can continue to be used after the roadway expansion construction,which simplifies the expansion construction process and doubles the increase utilization rate of bolts.