Shake Table Tests on Quality Evaluation Procedure for An Unsaturation Method for Liquefaction Countermeasures

Abstract eng:
Since an unsaturation or desaturation construction method for liquefaction countermeasures is inexpensive and simple, its introduction specially to housing sites have been examined after the 2011 off the Pacific coast of Tohoku earthquake. Although the mechanism of injecting air bubbles for unsaturation is almost understood, in-situ quality evaluation procedure of its introduction effectiveness has not been established yet. For the contribution to developing the quality evaluation procedure in situ, the authors conducted a shake-table test of saturated and unsaturated model grounds and performed field investigation by a dynamic cone penetrometer to recognize ground condition before shaking. The test and following consideration in this paper are based on the results of investigation using the dynamic cone penetrometer with a piezo drive cone (PDC) carried out at the experimental site for an unsaturation method and at a model ground in a container. The cone penetration tests obtained excess pore water pressure change and dynamic cone resistance, employed to evaluate the condition and variation of saturation of ground. In addition, the liquefaction behavior observed by accelerometers and pore water pressure transducers during shaking in the grounds is compared. Throughout the test results, the behavior of excess pore pressure change induced by cone penetration in the saturated and unsaturated grounds before shaking is identified. The consideration in this paper indicates the applicability of the quality evaluation procedure based on the mechanism of excess pore water pressure change.

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