<p><p><h2>Preferred Design Procedure</h2><p style="background: white; margin: 0in 0in 15.0pt 0in;"><span style="font-family: 'Arial',sans-serif; color: #646464;">No single document provides a comprehensive and through description of implementing a design process for vacuum preloading with and without PVDs. FHWA does provide guidance on two design methods for general PVD projects that can be used with vacuum preloading: the Conventional Method with PVDs and a Finite Element Model (FEM) Method. The Conventional Method is outlined by several documents including the 1986 FHWA <em style="box-sizing: border-box;"><span style="font-family: 'Arial',sans-serif;">Prefabricated Vertical Drains</span></em> manual (Rixner 1986) and the 2016 <em style="box-sizing: border-box;"><span style="font-family: 'Arial',sans-serif;">Ground Modification Methods, Volume 1 </span></em>(Schaefer et al. 2016), and is considered to be an established method. The FEM Method uses computer software to model the vacuum loading and the PVDs and is less established than the Conventional Method with PVDs. Both of these design methods are discussed in detail herein. Design guidelines and references for membrane material, pump, and PVD selection are also provided.</span></p>The Federal Highway Administration (FHWA) has design documents that cover both of the preferred design procedures for this technology. The documents are summarized below.</p><p><table class='tablepress' id='tablepress-315'><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 >Prefabricated Vertical Drains</td><td ><center>1986</td><td ><center>FHWA-RD-86-168</td><td ><center>Yes<sup>1</td></tr><tr><td >Ground Modification Methods, Volume 1</td><td ><center>2016</td><td ><center>FHWA NHI-16-027</td><td ><center>Yes<sup>2</td></tr></tbody></table><br><p class="disclaimer"><sup>1</sup> <a href="http://isddc.dot.gov/OLPFiles/FHWA/009762.pdf">http://isddc.dot.gov/OLP… class="disclaimer"><sup>2</sup> <a href="https://www.fhwa.dot.gov/engineering/geotech/pubs/nhi16027.pdf" target="_blank" rel="noopener">https://www.fhwa.dot.gov/engineering/geotech/pubs/nhi16027.pdf </a></p></p></p>
<p><p><h2>References</h2>Bergado, D.T., Chai, J.C., Miura, N. & Balasubramaniam, A.S. (1998). “PVD improvement of soft Bangkok clay with combined vacuum and reduced sand embankment preloading.” <em>Geotechnical</em> <em>Engineering. Journal</em>, Vol. 29, No. 1, pp. 95-122.</p><p>Chai, J. C., Hayashi, S., and Carter, J.P (2006). “Vacuum Consolidation and its combination with embankment loading.” Geotechnical Special Publication 152, Ground Modification and Seismic Mitigation, ASCE, 177-184.</p><p>Chu, J., Yan, S.W., and Yang, H. (2002). “Closure on discussion on ‘Soil improvement by vacuum preloading for and oil storage system’.” Geotechnique, Vol. 52, No. 2, 151.</p><p>Chu, J. and Yan, W. (2005a). “Estimation of degree of consolidation for vacuum preloading projects.” International Journal of Geomechanics, 5(2), 158-165.</p><p>Chu, J. and Yan, S.E. (2005b). “Soil improvement for a storage yard using a combined vacuum and fill surcharge preloading method.” Proc. Int. Conf. on Geotechnical Engineering for disaster Mitigation and Rehabilitation, Chu et al. (eds.), December 12-13, Singapore, 452-459.</p><p>Holtz, R.D. (1975). "Preloading by vacuum: current prospects." Transportation Research Record No. 548, Washington, D.C., 26-29.</p><p>Holtz, R.D. and Christopher, B.R., 1987, “Characteristics of Prefabricated Drains for Accelerating Consolidation”, <em>Proceedings of the Ninth European Conference on Soil</em> <em>Mechanics and Foundation Engineering</em>, Balkema, Vol. 2, Dublin, Ireland, August 1987</p><p>ISSGME TC-17 Ground Improvement Committee (2008). “Application of Ground Improvement: Vacuum Consolidation.” http://www.bbri.be/homepage/download.cfm?d type=services&doc=WGC_2_Vacuum_Consolidation_June_2008.pdf&lang=en</p><p>Jacob, A., Thevanayagam, S., and Kavazanjian, E. (1994) "Vacuum-Assisted consolidation of a hydraulic landfill", Vertical and Horizontal Deformations of Foundations and Embankments (GSP 40) Proceedings of Settlement ’94 held in College Station, Texas, June 16-18, 1994, pp.1249-1261</p><p>Masse, F., Spaulding, C.A., Wong, I.C. and Varaksin, S. (2001) “Vacuum consolidation: a review of 12 years of successful development.” Geo-Odyssey, ASCE, Virginia Tech, Blacksburg, VA</p><p>Rixner, J.J., Kraemer, S.R. and Smith, A.D. (1986). “Prefabricated Vertical Drains.” <em>U.S. Department of Transportation, Federal Highway Administration, Research, Development and Technology, Vol. I: Engineering Guidelines, Report No. FHWA/RD-86/168</em>.</p><p>Schaefer, V.R., Berg, R.R., Collin, J.G., Christopher, B.R., DiMaggio, J.A., Filz, G.M., Bruce, D.A., and Ayala, D. (2016). “Ground Modification Methods,” Federal Highway Administration, Washington, DC, FHWA NHI-16-027 (Vol. I), 386p. <a href="https://www.fhwa.dot.gov/engineering/geotech/pubs/nhi16027.pdf" target="_blank" rel="noopener">https://www.fhwa.dot.gov/engineering/geotech/pubs/nhi16027.pdf </a></p><p>Scott, R.F. (1963), Principles of Soil Mechanics, Addison-Wesley Publishing Co., Reading, Mass., U.S.A.</p></p>