<p><p><h2>Preferred Design Procedure</h2>There are separate design procedures for drilled and grouted soil nailing and hollow bar soil nailing. The Federal Highway Administration (FHWA) has a design document that covers drilled/grouted soil nailing. The document is summarized below.</p><p><table class='tablepress' id='tablepress-297'><thead><th><center>Publication Title</th><th><center>Publication
Year
</th><th><center>Publication Number</th><th><center>Available for Download</th></thead><tbody><tr><td >Geotechnical Engineering Circular No. 7 Soil Nail Walls</td><td ><center>2003</td><td ><center>FHWA0-IF-03-017</td><td ><center>Yes<sup>1</sup></td></tr></tbody></table><br><p class="disclaimer"><sup>1</sup> <a href="http://isddc.dot.gov/OLPFiles/FHWA/016917.pdf">http://isddc.dot.gov/OLP… a situation where the in-situ soil offers poor support and stand up time, hollow bar soil nailing may be a better option than drilled/grouted soil nails. The hollow bar soil nailing technology is different enough from traditional drill-and-grout soil nailing that the applicability of the design methods found in Lazarte et al. (2003) need to be considered. Key differences between design considerations of drilled/grouted soil nails and hollow bar soil nails are the pullout capacity and grouting process. The shape of the grout body can vary significantly along the length of the hollow bar soil nail. As a result, defining the area over which pullout resistance develops is difficult. While grout is an important component of drilled/grouted soil nail installation, the design of the grout and grouting process is critical for the hollow-bar soil nailing process. The grout is used as a medium for flushing the cuttings and supporting the borehole during installation. After installation the grout is responsible for transferring imposed loads between the reinforcement and the surrounding ground while protecting the steel reinforcement from corrosion. The effects of a poorly designed and/or executed soil nail installation will extend beyond the confines of the drill hole by grout permeation, and densification and fissuring of the surrounding soil. Grouts must be designed to provide high strength and stability while being pumpable. Typical water/cement ratios range from 0.45 to 0.6 by weight. Neat cement-water grout mixes are typically used. The water mixed with the cement should be potable water to minimize the potential for reinforcement corrosion. Experience shows the designed water/cement ratio has the greatest influence on grout fluidity and set properties. Variability in bond strength of hollow bar soil nails exists due to the varying installation techniques (Jésus Gómez, personal communication, February 10, 2010). Further research is necessary to establish preliminary design bond values and diameter magnification values.</p></p>
<p><p><h2>References</h2>Briaud, J.L., and Lim, Y. (1997). “Soil-Nailed wall under piled bridge abutment: Simulation and Guidelines.” Journal of Geotechnical and Geoenvironmental Engineering, Nov 1997, 1043-1050.</p><p>Bruce, D.A. (1993a). "In Situ Earth Reinforcing by Soil Nailing." Chapter 11, "Underpinning-and Retention." Edited by S. Thornburn and G.S. Littlejohn, Published by Blackie Academic and Professional, pp. 340-394.</p><p>Byrne, Porterfield, Cotton, Wolschlag, and Ueblacker. (1998). “Manual for Design and Construction Monitoring of Soil Nail Walls.” FHWA –SA-96-069R.</p><p>Fan, C. and Luo, J. (2007). “Numerical study on the optimum layout of soil nail designs.” Computers and Geotechnics 35 (2008), 585-599.</p><p>Gomez, J. (2009). “FHWA Hollow Bar Soil Nail (HBSN) Test Program.” 5th Annual Soil Nailing Seminar Charlotte, NC, February 2009. PowerPoint Presentation.</p><p>Lazarte, C.A., Elias, V., Espinoza, R.D., and Sabatini, P.J., (2003) <em>Geotechnical Engineering Circular No. 7 Soil Nail Walls, </em>FHWA0-IF-03-017, Federal Highway Administration, March, 2003.</p><p>Martin, J. (1997). “The design and installation of soil nail slope stabilization schemes using SNAIL.” in <em>Ground Improvement Geosystems-Densification and Reinforcement</em>, Eds. M.C.R. Davies and F. Schlosser, Thomas Telford Publishing, 398-406.</p><p>Pockoski, M. and Duncan, J.M. (2000). “Comparison of Computer Programs for Analysis of Reinforced Slopes.” Center for Geotechnical Practice and Research, Virginia Tech, CGPR #20, December 2000, 155 pages.</p><p>Rogbeck et al. (2003). “Nordic Guidelines for Soils and Fills.” The Nordic Geotechnical Societies Nordic Industrial Fund.</p><p>Samtani, N.C. and Nowatzki, E.A. (2010). “Hollow Bar Soil Nails Review of Corrosion Factors and Mitigation Practice.” FHWA, Publication No. FHWA-CFL/TD-10-002. August 2010.</p><p>Samtani, N.C. and Nowatzki, E.A. (2006). “Hollow Core Soil Nails State of the Practice.” FHWA, Publication No. Unassigned. April 2006. 55 pages.</p></p>