Field and Laboratory Verifications of Quality Evaluation Procedure for An Unsaturation Method for Liquefaction Countermeasures


Abstract eng:
Since an unsaturation or desaturation construction method for liquefaction countermeasures, such as injection of the mixture of micro-air bubbles and water, is inexpensive and simple, its introduction specially to housing sites have been developed after the 2011 off the Pacific coast of Tohoku earthquake. The workability of the method is clarified, while the completion or quality of its construction is evaluated only by partially checking saturation conditions using soil-moisture meter, resistivity logging and so on employed at observation and/or injection boreholes. In order to develop evaluation procedure of saturation condition so as to assess the introduced effectiveness of an air-injection method, authors carried out field investigation using the dynamic cone penetrometer with a piezo drive cone (PDC) at the reclaimed site along the Tokyo Bay in Chiba Prefecture where many liquefaction phenomena were observed in the earthquake. A PDC recognizes pore water pressure change in its penetration, which can be informative to understand change of saturation condition influenced by air injection. The investigation obtained the difference between excess pore water pressure change induced by cone penetration before and after air injection, verifying its applicability as evaluation procedure of saturation condition. In other words, it can be said that PDC investigation is appropriate for assessment of the construction management of the method. However, the quantification of the quality of improved ground has still been difficult. Therefore, following the field test, authors performed further PDC investigation at the laboratory model ground prepared in a small container to understand response characteristics of pore water pressure influenced by PDC penetration. The results of this investigation shows that similar observation in the field test is obtained even in the model with smaller confining pressure than that in the field. Also, increase of the peak values of pore water pressure when PDC penetrating into air-injected ground is confirmed. While further consideration is needed to understand this mechanism, pore water pressure change obtained by cone penetration is probably able to explain saturation conditions and help assess the effectiveness of an air-injection method as liquefaction countermeasures.

Contributors:
Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
Rights:
Text je chráněný podle autorského zákona č. 121/2000 Sb.



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 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 1529.:
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