<p><p><div><h2><strong>Project Summary/Scope:</strong></h2>A large, one story manufacturing facility (360,000 ft² footprint) was to be founded on alluvial deposits susceptible to liquefaction. Blast densification was used to densify the material.</p><p>Subsurface Conditions: Alluvial deposits extending as deep as 90 feet. The alluvial deposits consisted of very loose to loose, fine- to medium-grained sands with traces of silt and gravel. Evaluation of the soils revealed that loose zones existing from 20 to 50 feet deep would liquefy during a seismic event.</p><p>In areas where vibrations were not a concern, two decks of 7.5-pound Atlas Powder Primer was used in 50-foot square grids. In areas where vibrations were of concern, two decks of 5.4-pound Atlas Powder Primer were used in 30-foot square grids. Detonation of upper and lower decks was typically delayed by 8 ms. Greater delays were used to reduce vibrations. Blast densification was used as close as 175 feet from an existing wood-framed house.<br><h2>Alternate Technologies:</h2>Other ground improvement techniques considered include deep dynamic compaction and vibrocompaction.</p><p></div><h2>Performance Monitoring:</h2>Cone penetration tests were performed before and after blasting. Ground settlements ranged from 1 inch to 14 inches, averaging 5 inches. CPT results showed that the increase in strength sufficiently reduced the risk of liquefaction.<br><h2>Project Technical Paper:</h2>Schaefer, V., Abramson, L.W., Hussin, J.D., and Sharp, K.D. (1997). “Ground improvement, Ground reinforcement, Ground treatment: Developments 1987-1997,” Proceedings of sessions sponsored by the committee on soil improvements and geosynthetics of The Geo-Institute of the American Society of Civil Engineers in conjunction with Geo-Logan ’97, Geotechnical special publication No. 69. ASCE, New York.<br><h2>Date Case History Prepared:</h2>November 2012</p></p>