Study And Test On Preventing Slippage Failure Of Resin Anchor Rod In Coal Roadway By Expanding Bottom Filling

Due to the low strength and poor anchoring performance of coal roadway borehole surrounding rock,normal anchoring cannot meet the requirements of roadway surrounding rock control,resulting in the serious failure of resin bolt slip,which seriously restricts the safe and efficient mining of coal mine.Through referring to a large number of literature,it is found that the main causes of resin bolt slippage failure in coal alley are poor bonding ability and weak shear resistance between anchoring agent and borehole surrounding rock.In view of the above problems,a method to prevent the failure of anchor rod slippage is presented by means of theoretical analysis,laboratory test,numerical simulation and field test.Bottom-expanding and filling-in is to carry out an inverted wedge-shaped hole reaming at the bottom of the bolt hole,and then to fill the hole reaming part under the condition of retaining the original bolt hole.It is a technical method to improve the anchoring force of coal body,which improves the physical and mechanical properties of the borehole surrounding rock in the anchoring section and increases the bonding capacity of the anchoring interface between the anchoring agent and the borehole surrounding rock.Through theoretical analysis of the mechanical calculation formula of bottom reaming anchorage in the process of hole reaming,this paper establishes the mechanical analysis model of bottom reaming anchorage,and theoretically explains the feasibility of increasing the anchorage force of resin bolt by bottom reaming.Laboratory test results show that the ultimate bearing capacity of normal anchorage is 18.7k N,and that of double bottom filling is 17.41 k N,increasing by-6.9%.The ultimate bearing capacity of double bottom filling anchorage is 19.56 k N,with an increase of 4.6%.The ultimate bearing capacity of triple bottom filling is 35.1k N,with an increase of 87.7%;The ultimate bearing capacity of quadruple bottom filling is43.47 k N,with an increase of 132.5%;The ultimate bearing capacity of five-fold bottom filling is 52.1k N,with an increase of 178%.The drawing results show that the five times bottom filling anchorage.is the best and the anchoring force is the greatest.The results show that the axial force variation trend of the anchor with five-fold reaming is the same as that of the anchor with the bottom reaming with the bottom reaming is basically similar.The pullout force changes little and the increase curve is close to the level when the bottom filling anchorage is five times or above.The overall variation trend of displacement of each component decreases with the increase of reaming multiple.The changes of stress nebulogram of the same component in five times or more bottom filling anchorage are similar.Compared with normal anchorage,the stress increase curve presents almost horizontal changes.It is concluded that the comprehensive effect of five-fold bottom filling anchorage is the best.The field test results show that the total amount of deformation and the deformation velocity of the roadway roof with five-fold bottom expansion and bolting mesh support are less than the total amount of deformation of the roadway roof with two groups of normal supports.It is effective to prevent sliding failure of resin bolt.