American Society of Civil Engineers


In-Situ Desaturation Test by Air Injection and Its Evaluation through Field Monitoring and Multiphase Flow Simulation


by Mitsu Okamura, (Graduate, School of Science and Engineering, Ehime Univ., Matsuyama, 3 Bunkyo-cho, Matsuyama, 790-8577, Japan.), Masaya Takebayashi, (Research and Development Center, TOA Corporation, 1-3 Anzen-cho, Yokohama, 230-0035, Japan.), Katsuji Nishida, (Fudo Tetra Corporation, 7-2 Nihonbashi-koami-cho, Chuo-ku, 103-0016, Japan.), Nao Fujii, (Oriental Shiraishi Corporation, 2-1-1 Hirakawa-cho, Chiyoda-ku, 102-0093, Japan.), Motoharu Jinguji, (Planning Headquarters, Advance Industrial Science and Technology, 1-3-1 Kasumigaseki Chiyoda-ku, 100-8921, Japan.), Takehiko Imasato, (Nihonchikatansa Co. Ltd., 658-2 Hongo-cho, Funabashi, 273-0033, Japan.), Hideaki Yasuhara, (corresponding author), (Graduate, School of Science and Engineering, Ehime Univ., Matsuyama, 3 Bunkyo-cho, Matsuyama, 790-8577, Japan E-mail: hide@dpc.ehime-u.ac.jp), and Emiko Nakagawa, (Takamatsu Port and Airport Technical Investigation Office, MLIT, 1-6-1 Bancho, Takamtsu, 760-0017, Japan.)

Journal of Geotechnical and Geoenvironmental Engineering, Vol. 137, No. 7, July 2011, pp. 643-652, (doi:  http://dx.doi.org/10.1061/(ASCE)GT.1943-5606.0000483)

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Document type: Journal Paper
Abstract: Desaturation of ground by air injection attracts considerable attention in recent years as an innovative technique for a liquefaction countermeasure. Several research programs were conducted in laboratories regarding the related topics. This paper describes an in situ air-injection test that aims to examine the effectiveness of the air injection to desaturate ground and the validity of observation techniques to monitor the evolution of the unsaturated zone. In the test, air was injected from an air injector deployed in a targeted saturated-sand layer at a depth of 6 m. Observations revealed that the air-flow rate increased linearly with increasing air-injection pressure and the desaturated zone was generated within 4 m from the injection point. A 3-dimensional electric resistivity tomography technique was effective for evaluation of the desaturated zone. The degree of saturation of the in situ soil was observed by using high quality undisturbed samples obtained by the ground freezing method. The degree of saturation ranged from 68–98%, which was low enough to almost double the liquefaction resistance of the soil at the site. Numerical analyses were also conducted with a gas-liquid two-phase flow simulator to describe the evolution of the soil desaturation. Qualitatively, predictions show a relatively good agreement with the in situ measurements of the 3D electric resistivity tomography and are quantitatively compatible with the in-field degree of saturation measured indirectly by using the frozen soil samples. Actual liquefaction resistance was evaluated utilizing the undisturbed samples by conducting a triaxial test under cyclic shear conditions, which revealed that desaturated samples were indeed less susceptible to liquefaction compared with the fully saturated samples.


ASCE Subject Headings:
Saturation
Electrical resistivity
Radiography
Numerical models
Soil liquefaction
Monitoring

Author Keywords:
Degree of saturation
Desaturation
Electric resistivity
Tomography
Numerical simulation
Liquefaction resistance