Abstract: This paper reviews the insufficiency of anticorrosion performance of the bolts used in underground engineering and introduces both the structure and the anticorrosive mechanism of the multiple anticorrosive bolts. The experiments on corrosion resistance of both the dual and multiple anticorrosive bolts have been conducted under different corrosive environments, and the apparent change of bolts has been observed and the pullout capacity has been tested. The relationships of bond strength and sliding displacement between two types of anchor bar and cement mortar are also analyzed and compared. The analytical results indicate that because multiple anticorrosive bolts are enwrapped by casing in cement mortar, their pullout capacities in different corrosion environments are always greater than that of dual anticorrosive bolts, and the capacities grow more significantly with time. Sulfate crystallization and the drag effect between corrosion factors can cause a transient increase in pull-out capacity of the anticorrosive bolts, so that the bond strength of multiple anticorrosive bolts corresponding to same sliding displacement is higher, and the residual strength posterior to peak value is also greater than that of dual anticorrosive bolts. The above results can be used in the design of anticorrosive bolts in underground structures as well as the durability analysis during the later service period and also can provide valuable basic data for the study of corrosion resistance of anticorrosive bolts in practical engineering.

Key words: multiple anticorrosive bolts, corrosion environment, pullout capacity, bond strength, sliding displacement