Induced-Partial Saturation for Liquefaction Mitigation: Experimental Investigation
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 133, Issue 4
Abstract
The technical feasibility of a new liquefaction mitigation technique is investigated by introducing small amounts of gas/air into liquefaction-susceptible soils. To explore this potential beneficial effect, partially saturated sand specimens were prepared and tested under cyclic shear strain controlled tests. A special flexible liquefaction box was designed and manufactured that allowed preparation and testing of large loose sand specimens under applied simple shear. Partial saturation was induced in various specimens by electrolysis and alternatively by drainage-recharge of the pore water. Using a shaking table, cyclic shear strain controlled tests were performed on fully and partially saturated loose sand specimens to determine the effect of partial saturation on the generation of excess pore water pressure. In addition, the use of cross-well radar in detecting partial saturation was explored. Finally, a setup of a deep sand column was prepared and the long-term sustainability of air entrapped in the voids of the sand was investigated. The results show that partial saturation can be achieved by gas generation using electrolysis or by drainage-recharge of the pore water without influencing the void ratio of the specimen. The results from cyclic tests demonstrate that a small reduction in the degree of saturation can prevent the occurrence of initial liquefaction. In all of the partially saturated specimens tested, the maximum excess pore pressure ratios ranged between 0.43 and 0.72. Also, the cross-well radar technique was able to detect changes in the degree of saturation when gases were generated in the specimen. Finally, monitoring the degree of partial saturation in a long sand column led to the observation that after 442 days, the original degree of saturation of 82.9% increased only to 83.9%, indicating little tendency of diffusion of the entrapped air out of the specimen. The research reported in this paper demonstrated that induced-partial saturation in sands can prevent liquefaction, and the technique holds promise for use as a liquefaction mitigation measure.
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Acknowledgments
This research was funded by the National Science Foundation through the Geoenvironmental Engineering and Geohazard Mitigation Program, under Grant Nos. CMS-0234365 and CMS-0509894. The support of NSF and Program Director Dr. Richard J. Fragaszy is greatly appreciated. The writers thank Professor Carey Rappaport and Dr. Arvin M. Farid for their help in the use of the cross-well radar. Special appreciation is expressed to Mr. Richard Holt from NDT Corporation for his valuable insights into the field behavior of partially saturated sands.
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© 2007 ASCE.
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Received: Jun 3, 2005
Accepted: Jan 30, 2006
Published online: Apr 1, 2007
Published in print: Apr 2007
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