Study On Stress Corrosion Mechanism And Protection Technology Of Bolt Under High Temperature And High Humidity Environment

Under the condition of deep mining in a mine in western Shandong,the roadway is in a high ground stress,high ground temperature and high salt water environment for a long time.Such ’ three high ’ corrosion environment causes serious local or uniform corrosion of the supporting bolt in a short period of time,resulting in a sharp weakening of the supporting bearing capacity of the on-site bolt,a significant reduction in the mining safety factor,and a significant increase in the cost of roadway repair.This phenomenon is more prominent in deep high stress mines.In this paper,the stress corrosion mechanism and protection technology of bolt under high corrosion environment are taken as the research target.The stress corrosion damage characteristics and corrosion mechanism of bolt in a mine roadway in Luxi are investigated and analyzed,and the influence mechanism of temperature and humidity of roadway,mine water ion and surrounding rock composition on stress corrosion of bolt is determined.The influence of corrosion type and corrosion degree on the mechanical properties of bolt under stress corrosion was revealed by ABAQUS numerical simulation software.Accelerated corrosion tests of indoor bolts under different stress levels were carried out,and the physical and mechanical properties of corroded bolts were tested.The influence of time effect and stress level on the mass loss and mechanical properties of bolts in corrosion experiments was clarified.FLAC3 D was used to study the deformation and failure characteristics of roadway surrounding rock under the coupling condition of bolt corrosion and disturbance,and then the bolt protection technology for bolt stress corrosion in corrosive environment was proposed.The main conclusions of this paper are as follows :(1)Surrounding rock surface product composition,roadway,humidity and mine water ion concentration all promote bolt corrosion.On-site bolt corrosion is mostly manifested as stress corrosion formed by pitting development under stress loading conditions.The stress corrosion of underground bolt belongs to anodic dissolution type,and its corrosion process presents the stage characteristics of ’ oxide film formationcracking-dissolution ’.(2)Corrosion test shows that the corrosion degree of anchor rod increases with the increase of corrosion cycle and stress level,which is manifested by the increase of the number of corrosion pits,the deepening of corrosion crack depth and the linear increase of mass loss.The corrosion rate decreases first and then increases with the increase of corrosion time,and the corrosion rate continues to accelerate with the increase of stress.In addition,the mechanical properties such as the elongation of the anchor rod and the yield strength of the ultimate strength show a downward trend affected by corrosion,but the decline rate of the mechanical properties gradually slows down.(3)The numerical analysis shows that the crack angle caused by corrosion has a great influence on the mechanical properties of the bolt,and the bearing capacity of the bolt decreases with the increase of the crack and the axial inclination angle of the bolt.In addition,corrosion has the greatest influence on the fracture strain of various mechanical properties of the bolt,and the fracture position of the bolt often occurs at the defect of the corrosion characteristic rod.(4)It is found that under the coupling condition of bolt corrosion and disturbance,the deformation of roadway surrounding rock increases greatly,and the range of plastic zone of surrounding rock expands significantly,which indicates that stress corrosion under the influence of disturbance leads to a sharp decline in bolt support efficiency.Therefore,it is necessary to pay attention to bolt stress corrosion in field engineering.(5)By comparing the apparent damage,mass loss rate and mechanical properties of bolts under different corrosion protection technologies,it is shown that the coating of bolts under group E(isolation method)protection measures is basically complete and the quality is basically not reduced,followed by group C(material modification method).The comprehensive anti-corrosion effect of anode compensation + anticorrosion coating is better than that of single anti-corrosion measures.This thesis has 46 figures,12 tables and 90 references.