An August 2010 FHWA Central Federal Lands report on corrosion of hollow bar soil nails has recently been made available on the NCS Consultants, LLC website. The authors of the report are Naresh Samtani and Ed Nowatzki of NCS. From the abstract:
Hollow bar soil nails (HBSNs) have been used in the United States in earth retention systems for over 10 years. HBSNs are commonly used in place of solid bar soil nails (SBSNs) when the solid bar installation would require temporary casing of the hole. A state-of-the-practice document was prepared by FHWA in 2006 to identify (a) the various peculiarities of HBSNs in comparison with conventional SBSNs, and (b) areas of further research, evaluation and testing that would help agency personnel and design professionals understand the potential of HBSNs as a mainstream technology for permanent soil nail applications. This report concentrates on one of the specific areas of study identified in the 2006 report as related to development of corrosion mitigation guidance.
This report presents the results of an industry-wide survey including agencies, designers, consultants, manufacturers and contractors related to installation of HBSNs and practices with respect to corrosion aspects. Based on the responses it was found that a lack of guidance on corrosion protection is limiting the use of HBSNs for permanent applications in corrosive environments. There are numerous contributing factors that may lead to corrosion of HBSNs. These factors are identified in this report along with a review of the current corrosion mitigation guidance. Parameters to be evaluated in formal corrosion studies are outlined. Finally, recommendations for interim corrosion mitigation guidance and further studies are provided.
[Source: NCS Consultants, LLC. Image: FHWA]