<p><p><figure id='attachment_3612' style='max-width:372px' class='caption aligncenter'><img class="wp-image-3612 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Schematic of site conditions." width="372" height="357" /><figcaption class='caption-text'> Schematic of site conditions. (Mankbadi et al., 2004; With permission from ASCE)</figcaption></figure></p><p><div><h2>Project Summary/Scope:</h2>The project involved the replacement of a bridge on US Route 9 over Nacote Creek near Galloway Township, New Jersey. The new bridge required a shift in the alignment of the road resulting in the new alignment partially over fill material from the old alignment and partially on marshlands. Without any soil improvement, the expected differential settlement between the existing alignment and the new embankment over the marsh was 1.2 meters.</p><p>Subsurface Conditions: The marshlands consisted of 3 to 6 meters of organic silt and peat sediments. Underlying the organic silt/peat layer was a quartz sand and gravel with silts and clay pockets which was underlain by the Cohansey Sand formation (dense sand, ϕ’ = 37°).</p><p>The south approach embankment consists of 10-meter high by 16-meter wide back-to-back MSE walls. Design of the Vibro-Concrete Column (VCC) system was completed using NAVFAC DM-7.2. The ultimate capacity of each VCC was 1100 kN (250 kips) and spacing was chosen to limit the column loads to 580 kN (130 kips) corresponding to a factor of safety of 1.9 against bearing capacity failure. The column lengths were 8.5 meters, extending to the Cohansey Sand formation. Load tests confirmed ultimate capacities of 1,800 kN and 2,600 kN using the Davisson (1972) and Kyfor et al. (1992) criterion respectively.</p><p>The diameter of the VCCs was 457 mm with upper and bottom bulbs ranging from 600 to 750 mm.<br><h2>Alternate Technologies:</h2>Other options considered were preloading, which was eliminated due to excessive construction easement requirements; stone columns, which would result in intolerable differential settlements; and deep mixing, which was eliminated since lab tests showed that the maximum compressive stress of the soil-cement-sand mixtures was not adequate for embankment support.<br><h2>Complementary Technologies Used:</h2>MSE Wall</p><p><figure id='attachment_3614' style='max-width:500px' class='caption aligncenter'><img class="wp-image-3614" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Schematic diagram showing a typical cross section of vibro-concrete columns installed in a project." width="500" height="508" /><figcaption class='caption-text'> Typical cross section. (Mankbadi et al., 2004; With permission from ASCE)</figcaption></figure><h2>Performance Monitoring:</h2>Settlement platforms, probe extensometers, inclinometers, piezometers, and strain gages attached to the geotextiles were used to monitor the VCC system performance. The maximum settlement of the embankment was 40 mm.<br><h2>Project Technical Papers:<strong> </strong></h2>Mankbadi, R., Mansfield, J., Wilson-Fahmy, R., Hanna, S., and Krstic, V. (2004). “Ground improvement utilizing vibro-concrete columns.” <em>GeoSupport 2004</em>. 1-12. <a href="http://ascelibrary.org/doi/abs/10.1061/40713%282004%2955">http://asceli…, R., Hanna, S., and Mankbadi, R. (undated). “Approach embankment supported by geotextile reinforced sand platform over vibro concrete columns—a case study.”<br><h2>Date Case History Prepared:</h2>November 2012</p><p></div></p></p>