Experimental Research On Corrosion Durability And Protection Technology Of Rock Bolts In High Corrosion Environment

Bolt support is the foundation of the surrounding rock control of mines and tunnels in our country,and it is also an effective technical guarantee for the safe mining of deep mines in our country.However,as coal mining enters the kilometer mining stage,many mines are facing the problem of premature failure of anchoring materials under"high temperature,high humidity,and high water spray"environments.In this paper,the method of field survey and physical and chemical analysis is used to study the serious corrosion phenomenon of mine anchoring materials from the perspective of corrosive environment.It is pointed out that the serious corrosion of anchoring materials is the composition and structure of the surrounding rock of the roadway,the atmosphere of the mine,high ground temperature,high stress,and the mine.The coupling effect of water and other factors reveals the electrochemical corrosion mechanism of the anode dissolution and the cathode oxygen absorption reaction of the anchor rod.The electrochemical workstation was used to test the corrosion tendency and corrosion rate of the steel strip sample in mine water,and the effect of PH on the corrosion rate and corrosion tendency under the same anion composition was studied.Based on the analysis of the corrosion mechanism of the bolt and the cause of the serious corrosion of the bolt,the salt spray test box is used to simulate the downhole high temperature and high humidity environment,and the more corrosive Cl~-is selected as the main anion of the accelerated corrosion test solution.Through tensile tests,the changes in yield strength,ultimate load,and breaking elongation of bolts under different corrosion times were studied,and the changes in corrosion characteristics and corrosion rates with corrosion time were analyzed.The FLAC3D numerical calculation software is used to determine the failure of roadway bolts under different damage levels after the yield load of the bolts corroded and the influence on the plastic zone of the roadway surrounding rock.Finally,based on the above research,five different bolt protection measures were designed,and corrosion resistance tests under high temperature,high humidity,and high corrosion environments were carried out.The main research conclusions are as follows:(1)The yield load,ultimate load,and elongation at break of high-strength bolts and equal-strength bolts continue to decrease with the increase of corrosion time,and a significant decrease occurs at 21 days;the corrosion rate of equal-strength bolts gradually tends after a rapid decline For stability,the corrosion rate of high-strength bolts first decreases and then slowly increases.(2)The corrosion degree of anchor rods increases with time.The surface of equal-strength anchor rods appears obvious pitting corrosion,pitting corrosion and cracks after 42 days of corrosion,while high-strength anchor rods appear obvious pitting corrosion,pitting corrosion after 21 days of corrosion.The phenomenon,and the mechanical performance has decreased significantly,indicating that the local pitting and pitting corrosion of the rod body will seriously affect the mechanical performance of the bolt.(3)FLAC3D is used to study the breaking sequence of the anchor rod under different reduction degrees of the yield load after corrosion and the influence of the fracture on the plastic zone of the surrounding rock.It is found that when the yield strength is reduced by 20%,the shoulder anchor breaks first;When the yield load is reduced by 50%,all bolts are broken;the maximum damage depth of the plastic zone of the surrounding rock of the roadway increases with the decrease of the yield load in the horizontal direction,but there is no obvious change in the vertical direction.(4)After the anchor rod is protected,after 42 days of accelerated corrosion test,the integrity of the surface coating of the anchor rod with the protection treatment of group C is good,the mechanical properties of the anchor rod are not weakened,and the protection effect is the best;The anchor rods treated with B protective coating have poor corrosion resistance;the E group anchor rods in electrochemical protection have better protection effects in the short term.There are 64 figures,20 tables and 76 references.