Summary of Example Specifications

Reference(s):
DFI (2009)
This specification can be modified to serve as a performance approach, method approach, or combination specification. In addition, a hollow bar soil nail supplement is provided. The specification is easy to read, logically ordered, and provides clear instructions for completing the work. There are no conflicting statements in the specification. However, the specification does not state what design method to use. This is left up to the contractor, which will make comparing bids difficult for the owner.
Overall performance requirements are not provided in this specification. The specification, as presented, is intended to take advantage of the contractor’s experience so that a large amount of responsibility lies with the contractor. The specification does not require overly elaborate or expensive construction methods. This specification clearly outlines the nail testing procedures and provides construction method requirements (combined performance/method specification). The specification also provides good commentary about how and why the QC/QA methods are required. This specification contains the sections required for a combined method/performance specification. ASTM material standards are clearly outlined. However, the specification does not state what design method to use or what are the required factors of safety.

Reference(s):
Lazarte et al. (2003)
The specification contains helpful commentary. This specification expressly forbids the use of hollow bar soil nails. The specification is easy to read, logically ordered, and provides clear instructions for completing the work. There are no conflicting statements in the specification. The specification fairly allocates the risk between the contractor and owner. The specification does not provide information about the subsoil conditions, shotcrete facing, or wall instrumentation. However, supplemental specifications for shotcrete facing and instrumentation are provided in Lazarte et al. (2003). The specification does not require overly elaborate or expensive construction methods. This specification outlines typical method and performance verifications for soil nailing. This specification alone is lacking certain sections (subsurface conditions, instrumentation, design methodology). However, it is intended to be used in conjunction with other guide specifications in the FHWA documents (shotcrete and instrumentation specification).

Reference(s):
Lazarte et al. (2003)
The specification contains helpful commentary. The specification is easy to read, logically ordered, and provides clear instructions for completing the work. There are no conflicting statements in the specification. The risk is fairly allocated between the owner and contractor. The contractor is responsible for producing a design that is then constructed to satisfy specification requirements. The specification does not provide information about the subsoil conditions, shotcrete facing, or wall instrumentation. However, supplemental specifications for shotcrete facing and instrumentation are provided in Lazarte et al. (2003). The specifications do not require overly elaborate or expensive construction methods. This specification refers the reader back to the FHWA Procedural Specifications for Soil Nail Walls with some changes to allow more freedom of contractor methods. The specification therefore contains the same performance QC/QA as the FHWA Procedural Specifications for Soil Nail Walls. This specification contains the necessary modifications to the Procedural Specifications to create a pure performance-based specification.