ABSTRACT
Soil nails are commonly installed in soils with complex physical and chemical composition; they are also subjected to variations in environmental conditions, both spatially and temporally. Potential degradation of soil nails by corrosion may adversely affect the long-term performance of a soil nailed structure. Durability is therefore an essential consideration and design requirement of a soil nailed structure. In this chapter, the fundamental mechanism of corrosion, types of corrosion, factors affecting corrosion rate, various corrosivity classification systems for the ground, and the range of associated corrosion protection measures for soil nails are presented. Reference is made to the extensive studies carried in the United States, the UK, and Hong Kong on corrosion of buried steel. The results of these studies indicate that pitting corrosion is more hazardous than uniform corrosion as the former has a corrosion rate which is an order of magnitude greater than the latter. Depending on the corrosivity of the ground, and the nature and service life of the nailed structure, it is common practice that appropriate corrosion protection measures are provided to soil nails so that their long-term performance would not be jeopardized. The practices adopted by various places, including France, Germany, the UK, the United States, the Nordic Countries, Japan, and Hong Kong, have been reviewed and discussed. Apart from steel, other materials with good durability performance, such as fiber reinforced polymers (FRP), are being adopted for some soil nailing projects. Amongst these advanced materials, GFRP reinforcing bars have been used mostly as temporary soil nails for stabilizing excavations.
