Study On The Anchorage Effect Of Screw Bolt In Coal Ribs

Screw bolt,as a new kind of anchorage product,has a strong adaptability to the loose coal roadway support.It not only provides an alternative method for solving the safety risk caused by the failure of the resin anchorage system under the specific geological conditions,but also help to release the support effectiveness of the roadway tunneling process.However,at present,Screw bolt has not attracted enough attention in the field of coal roadway support,and the mechanism of its anchorage generation,work and failure is not clear.This paper focuses on the whole process of anchoring,through theoretical analysis,as well as field and laboratory test methods,to research on the Screw bolt's mechanism.In this research,three kinds of anchoring forces generating ways are mentioned,and the factors affecting the anchoring effect are tested.The relationship between the installation process,screw structure height,and the length of screw section is confirmed.After that the failure characteristics of the Screw bolt's anchorage system is studied.Finally,through field test,the evolution law of the anchoring force in the coal under the condition of surrounding rock stability and mining is analyzed.The main conclusions are as follows:?1?Under the premise of ensuring the strength and rigidity of anchor,reducing the anchor's diameter D,screw structure groove depth h and controlling the u₀ will help the anchor drill in and generate the anchoring force.?2?Screw bolt's anchoring force is first increased and then decreased with the diameter of the guide hole.The anchorage effect reach the maximum is when the guide hole reserve value between 30mm⁶0mm.The length of the screw structure section should take the screw height,the parameter of the guide hole and coal's physical mechanical characteristics into consideration.?3?The Screw bolt's no-live load stage failure process is mainly subjected on the shear resistance formed by the inlay groove.While the loading stage's failure process is divided into four stages:interface voids,interface closure,interfacial shear slip and interfacial debonding failure.Based on the damage mechanics theory,the critical values of the failure of anchor system in the no-load stage and the loading stage are obtained.?4?Under the condition of surrounding rock stability,the preload force makes the friction force of Screw bolt reach its peak value.As time goes on,the working resistance of anchor decreases first and then stabilizes.Under the mining condition,the working resistance of the Screw bolt tends to increase with the adjustment of mining stress,and when the surrounding rock of the roadway becomes stable,then the working resistance tends to be stable.