SGER: Development of Field Delivery System of Oxygen Bubbles for Seismic and Geoenvironmental Hazard Mitigation

Northeastern University, Boston MA

Investigators

Abstract

Mitigation of liquefaction-induced damages to the built environment continues to be an important priority and a major challenge in civil engineering. Current soil improvement methods to safeguard against liquefaction are often very expensive and their applications are limited to new sites. There is an urgent need to develop cost-effective liquefaction mitigation measures that can be applied to new sites as well as sites where structures exist. The PI and CO-PI have been conducting research on developing an innovative method for liquefaction mitigation based on inducing partial degree of saturation in otherwise fully saturated liquefiable sands. The research to date has demonstrated the technical feasibility of the method. Laboratory tests have led to the conclusion that introduction of gas bubbles in sand, thus reducing its degree of saturation, prevents the occurrence of liquefaction. While the feasibility of induced partial saturation as a potential liquefaction mitigation measure has been successfully demonstrated, it is the PI and CO-PI?s ultimate goal to further advance this mitigation measure, prove its feasibility through field research tests so that the professional engineering community considers its application in practice. This will require implementation of a comprehensive research program with testing under large scale laboratory and field conditions. However, such a research program can not be embarked nor funding can be secured unless two distinct and important research goals are first achieved. This SGER award focuses on these two research goals. The first goal of the proposed research is to devise a delivery system that can generate gas bubbles in fully saturated sands that can be implemented with high likelihood of success in the field. This gas delivery system should be practical and be able to reduce the degree of saturation of sands rapidly and uniformly. The second important goal is to devise a field testing technique that can be used to assess the effectiveness of the gas delivery system leading to validation of partial degree of saturation, as well as the uniformity of the site remediation. Results from preliminary investigations suggest that oxygen bubbles can be generated within sands through the introduction of chilled water with dissolved ?Efferdent? (primarily sodium perborate), or through chilled hydrogen peroxide with an added catalyst to release oxygen when temperature of the fluid rises. Also, it is apparent that the use of a piezocone and measurement of excess pore pressures developed during the penetration of the piezocone into the sand can be a practical and rapid way of validating partial degree of saturation and its uniformity. These exploratory research activities will be conducted using the SoilBed facility of the Center for Subsurface Sensing and Imaging Systems (NSF-ERC-CenSSIS) The outcome of this research can help advance efforts at developing a cost-effective liquefaction mitigation measure that can have world-wide impact on safety and protection of property from earthquake hazards. Development of cost-effective oxygen delivery system can also help in situ bioremediation method to be more widely implemented in practice. The research is collaboration between faculty and students in the fields of earthquake engineering and geoenvironmental engineering. Such interdisciplinary collaborations have led to innovative ideas and continue benefiting undergraduate and graduate students engaged in the research