Study On Stress Corrosion Failure And Prevention Measures Of Anchorage Materials In Deep Mine

The problem of durability degradation and fracture of anchoring materials in deep mines has always been one of the important problems in the development and utilization of deep resources.The redistribution of the original rock stress caused by the underground mining process makes the corresponding stress change dynamically in the service state of the anchoring material.This leads to the corrosion failure of anchorage materials.This process is a temporal coupling of hydrogen-induced stress corrosion and anodic dissolution.This is extremely dangerous for underground engineering.At present,the domestic research on the corrosion of anchoring materials for underground mining is relatively shallow,and the anti-corrosion method is even poorer.Therefore,in order to prolong the service life of the anchoring material in the service environment,this study firstly analyzed the corrosion failure characteristics of the anchoring material through laboratory service environment simulation.The study found that the corrosion failure of the anchoring material is related to the corrosive medium contained in the service environment.Based on this,the experimental design concept that the anticorrosion of anchoring materials in mine service needs to isolate the metal part from the water corrosive environment,or prolong the contact time as the main anticorrosion goal is determined.Through research,it is determined that the anchoring material is protected by coating anti-corrosion means.Finally,laboratory experiments were carried out on several coatings that were relatively well studied and had a certain inhibitory effect on hydrogen-induced stress corrosion cracking.In this study,the service environment materials of the frequently-failed bolts in a coal mine were collected,and the collected environmental materials were simulated in the laboratory in the form of "corrosion cells".The experiment found that the ore body or surrounding rock in the environment increased the ion solubility of the groundwater solution through ion exchange,which indirectly accelerated the corrosion of the bolt.This observation proved that the ion concentration in the solution was positively correlated with the corrosion rate.Corrosion is a long-term process.After 3 months of experiments,most of the corrosion products are formed at the ends of the threads and bolts,as well as the parts surrounded by clay and coal,reflecting that minerals can accelerate the corrosion of bolts.Compared with the corrosion medium only deionized water,the tensile strength of the bolt after corrosion in the experimental environment containing clay or coal is reduced.The research shows that the corrosion failure of the anchoring material is related to the corrosive medium contained in the service environment.The corrosion failure is not caused by groundwater alone,but by the synergy of the multi-attribute environment of the mine under complex geological conditions.Minerals in the environment change the concentration of ions in the solution through ion exchange and indirectly accelerate the corrosion of bolts,thereby reducing the mechanical properties of the anchoring materials.In order to explore the anti-corrosion properties of different coatings on deep anchoring materials,the anti-corrosion properties of seven coatings were studied in this experiment including hot dip galvanized,polyurethane,epoxy coating,Everbrite,Silvershield,chlorinated rubber,alkyd.After several weeks of experiments,it was found that a large number of subcritical cracks occurred on the uncoated metal surface,and the cracks showed a trend of large expansion and convergence.The anchoring material with coating protection basically did not form subcritical cracks,and the fracture of each sample showed a typical tearing morphology(TTS).The anti-corrosion properties of the coatings shown in the experiment are quite different,among which the epoxy coating and the chlorinated rubber have strong anti-corrosion ability,and the galvanized layer has the weakest anti-corrosion mechanism due to the sacrificial level.Through the analysis of the results of this experiment,it is found that the low toughness of some coatings may not be universal in the mine environment,but the research and development of coating materials has proved that the effect of the coating is related to the curing agent and additives.Monolithic coating materials have limitations,and composite coatings still require a certain period of development.Although each coating eventually failed,the application of the coating greatly improved the life of the samples in the experiment,and the experimental results provided theoretical and technical support for the future development of these coatings in mines.