Liquefaction Forum a Success The DFI Ground Improvement Committee’s forum on the state-of- the-art of liquefaction analyses and mitigation attracted over 80 attendees to St. Louis, Mo., in April. This event was a first for the committee, which invited a panel of internationally-recognized researchers to present and discuss current research results related to the consequences and mitigation of earthquake-induced liquefaction. The forum was attended by engineers and practitioners nationwide. The successful event was made possible through the efforts of committee members Dr. Tanner Blackburn, Billy Camp, Jeff Hill, Tim Siegel, Lyle Simonton and Marty Taube (chair). Professor Edward Kavazanjian of Arizona State University opened the forum with an overview of the potential impacts of earthquake-induced liquefaction, including settlement, bearing capacity, downdrag, loss of lateral support, lateral earth pressures on retaining structures, and lateral spreading and flow sliding. He reviewed the drainage, densification, and reinforcement and stabilization measures used for mitigation, illustrated through examples from over the past 50 years. Brady R. Cox, professor at the University of Arkansas, discussed key liquefaction lessons learned from post-earthquake reconnais- sance of the M7.0 Haiti Earthquake, the M7.1 Darfield New Zealand Earthquake, the M6.1 Christchurch New Zealand Earthquake, and the M9.0 Tohoku Japan Earthquake. This work was conducted through NSF-funded Geotechnical Extreme Events Reconnaissance (GEER) Association. His presentation highlighted the substantial economic impact of soil liquefaction damage in New Zealand and Japan, two countries with high-quality seismic design standards. Professor Ross Boulanger, University of California Davis, discussed the current state of the practice of how to account for shear reinforcement effects for liquefaction mitigation. Russell Green, professor at the Virginia Tech discussed mitigation of liquefaction through use of stone columns to dissipate excess pore pressures in loose, saturated sandy soil deposits. Kyle Rollins, professor, Brigham Young University presented his research program aimed at evaluating the performance of full-scale foundations subjected to blast-induced liquefaction. He presented lateral and axial perfor- mance (including downdrag) results from foundation tests on drilled shafts, single piles and pile groups. Professor Scott Olson, University of Illinois, spoke about the current state of the practice, and offered a Newmark sliding-block approach using liquefied shear strength ratios to evaluate lateral spreading displacements. Silas Nichols of the Federal Highway Administration summarized the FHWA’s updated manual, LRFD Seismic Analysis and Design of Transportation Geotechnical Features and Structural Foundations, and the recommended approach to liquefaction mitigation. The presen- tations were followed by questions and a reception. Topics ranged from general ground improvement practices to in-depth liquefaction analyses and approaches. The Forum also attracted eight exhibitors. DEEP FOUNDATIONS • JULY/AUG 2012 • 25
