0234365, Mishac Yegian, Northeastern University "Air Entrapment for Liquefaction Mitigation"
This action is to support a study of the scientific and technical feasibility of an innovative approach for mitigating soil liquefaction.
Liquefaction-induced damage to the built environment can be catastrophic. During the past four decades, intensive efforts have been made to understand the mechanism of liquefaction, and to develop procedures for analyzing the liquefaction potential at a site during a given seismic event. While research on liquefaction continues, geotechnical engineering practice has developed various techniques for site improvement that can mitigate the potential effects of liquefaction. Such mitigation measures are expensive, and often can only be utilized for a new project. Mitigating the liquefaction-induced damage to an existing structure in an urban community remains a major challenge.
The concept is to introduce air in a saturated sand deposit to increase its resistance against liquefaction. Laboratory and field experiences suggest that only slight amounts of air in the voids of otherwise fully saturated sands (enough to reduce the degree of saturation by 1 to 2%) can significantly increase the liquefaction strength, and decrease the shear wave velocity. Hence, through air entrapment, a new or an existing site can potentially be improved to resist liquefaction, and through shear wave velocity measurements, its adequacy can be verified.
The research has a number of specific objectives that are aimed at providing a preliminary understanding of the behavior of air-entrapped sands, and of identifying important areas for future research that would be needed to advance the concept to a fully developed and practical measure for liquefaction mitigation. The objectives of the research can be stated in the form of questions as follows: 1. How can air be introduced in loose saturated sands? 2. How can samples of varying degrees of saturation (from 95 to 100%) be prepared? 3. How can the degree of saturation be measured accurately (up to 0.1%)? 4. How will air entrapment affect the liquefaction strength? 5. How are other soil properties influenced by the presence of air? 6. How does the grain size distribution and angularity of the sand influence the above results? 7. How long can air stay trapped under different flow gradients?
The research will be a significant contribution to the development of cost-effective measures for liquefaction mitigation. It will also have a broader impact on improving the ability to reduce the expected losses to a community from an earthquake. The research will draw upon the expertise in the geo-environmental field that uses air injection for remediation.
