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

Okamura, Mitsu; Takebayashi, Masaya; Nishida, Katsuji; Fujii, Nao; Jinguji, Motoharu; Imasato, Takehiko; Yasuhara, Hajime; Nakagawa, Emiko

doi:10.1061/(asce)gt.1943-5606.0000483

Cited by 125 publications

(53 citation statements)

References 20 publications

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“…The test results presented here prove that the desaturation state can be stable under hydrostatic conditions. This result agrees with Okamura et al (2011), which showed that the desaturation state in soil ground below groundwater table can be sustained over more than 20 years. But the desaturation state becomes unstable under constant water flow.…”

Section: Stability Of Desaturation State In Soilsupporting

confidence: 82%

“…The desaturation effect of soil can also be attained by water electrolysis, that is, to apply an electric current through soil so that pore water can be decomposed to oxygen and hydrogen gases (Yegian et al, 2007). Direct air injection is a straightforward method and has been tested by Okamura et al (2011) in a field experiment. The degree of saturation of sandy ground was successfully reduced to 68%-98% within a 4-m range from the injecting point.…”

Section: Introductionmentioning

confidence: 99%

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Mitigation of soil liquefaction using microbially induced desaturation

Chu

et al. 2016

J. Zhejiang Univ. Sci. A

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Soil liquefaction can cause disastrous consequences to buildings and human lives. Regular countermeasures against soil liquefaction are often overly expensive for normal buildings and structures. This could be the major reason that liquefaction induced damage is still widely encountered in large-and mid-size earthquakes in recent years. In this paper, a new method for the mitigation of soil liquefaction using the microbially induced soil desaturation is proposed and tested. The desaturation effect in soil is achieved by the generation of nitrogen gas produced from the microbial denitrification process. Some major issues related to this method are experimentally investigated. These include soil desaturation procedures, shapes and distribution of gas bubbles in soil, mechanical responses and liquefaction resistance of desaturated soils, and stability of gas in soils. The desaturation treatment of soils is made simply by introducing denitrifying bacteria and a desaturation solution into soil pores by mixing, flushing, or injection. The degree of saturation can be reduced as the microbial reaction proceeds. Experimental results show that the final degree of saturation is related to the initial nitrate concentration added to the soil: the higher the concentration of nitrate in the desaturation solution, the lower the degree of saturation that can be achieved. The existence of gas bubbles in soil is evidenced by computer tomography (CT) technology. The CT images reveal that gas is in the form of small pockets which has a size a little larger than the mean size of sand grains. It is shown in the shaking table tests that microbially induced desaturation can effectively improve the liquefaction resistance of soil by showing a much lower pore pressure generation, much smaller volumetric strain, and much smaller settlement of the structure in desaturated soil, as compared with those in saturated soil. Triaxial consolidated undrained tests reveal that the desaturation treatment of soil can improve the undrained shear strength of loose sand. The stability of gas is tested under hydrostatic and water flow conditions. The gas phase is stable under the hydrostatic condition, but unstable under water flow conditions. So measures ought to be taken to prevent steady flow in practice.

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Section: Stability Of Desaturation State In Soilsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Mitigation of soil liquefaction using microbially induced desaturation

Chu

et al. 2016

J. Zhejiang Univ. Sci. A

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“…In recent years, some researchers have been investigating liquefaction mitigation techniques that involve the artificial introduction of gas bubbles and creating partially saturated zones in the liquefiable soil deposits. Some of these techniques are water electrolysis (Yegian et al 2007), drainage-recharge (Takemura et al 2008) and air injection (Okamura et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Centrifuge testing to evaluate the liquefaction response of air-injected partially saturated soils beneath shallow foundations

Zeybek

Madabhushi

2016

Bull Earthquake Eng

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Earthquake-induced liquefaction of saturated soils continues to cause severe damage to structures with shallow foundations. In recent years, artificially reducing the degree of saturation and forming partially saturated zones within saturated soils has been proposed as a liquefaction mitigation technique. This study experimentally investigates the liquefaction response of air-injected partially saturated soils beneath shallow foundations. A series of centrifuge tests were conducted on the shallow foundations with different bearing pressures. The results of the tests show that the generation of excess pore pressures and consequent liquefaction-induced settlements of shallow foundations were a strong function of the degree of saturation. Forming spatially distributed partially saturated zones in the liquefiable soils limited the development of high excess pore pressures and liquefaction susceptibility of soils, particularly at the higher confining stresses. The reduction in the degree of saturation of soils decreased the depth of liquefied soil layer, and increased the resistance of soil to the bearing capacity failure. On the other hand, the decrease in the degree of saturation of liquefiable soils led the larger accelerations to be transmitted to the foundations through unliquefied soil zones. It is therefore concluded that use of air-injection as a liquefaction mitigation measure does reduce structural settlements, but will have the consequence of larger structural accelerations.

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“…Debido a que se producen y liberan grandes cantidades de gas durante el proceso de densificación, y una parte de este gas permanece atrapado en el suelo por muchos años (Finno, Gallant y Sabatini, 2016;Okamura, Ishihara y Tamura, 2006;Okamura et al, 2011;Vega-Posada, 2012;Yegian, Eseller-Bayat, Alshawabkeh y Ali, 2007), los depó-sitos de arena densificados con explosivos pueden ser clasificados como suelos gaseosos (Ramos, Felipe y Vega-Posada, 2016;Vega-Posada, Finno y Zapata-Medina, 2014). Los suelos gaseosos son un tipo especial de suelo donde el gas (i.e., aire) existe en una condición ocluida y esta fase gaseosa no está conectada con la atmósfera (Nageswaran, 1983).…”

Section: Introductionunclassified

Efecto del gas en la velocidad de onda de corte de suelos arenosos densificados con explosivos

Vega-Posada

Ramos-Cañón

Aristizábal

2017

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InvestIgacIón ResumenContexto: Los ensayos de velocidad de onda de corte (Vs), son comúnmente utilizados para estimar el incremento en resistencia de suelos densificados con explosivos. En algunos casos históricos los ensayos de Vs realizados después del proceso de mejoramiento de suelo no muestran un incremento significativo en la resistencia del suelo, aun cuando la superficie del terreno se asienta más de 0,50 m. Se cree que esta respuesta se debe a la presencia de gas en la masa de suelo. Método: En este trabajo se presentan los resultados de ensayos triaxiales monotónicos realizados en muestras de suelos arenosos gaseosos medianamente densos, para evaluar el efecto del gas ocluido en la respuesta a la velocidad de onda de corte en arenas densificadas con explosivos. Muestras de arena fueron recolectadas de un depósito de arena suelta localizado in Carolina del Sur, Estados Unidos, y el cual fue densificado in situ con explosivos. Las muestras fueron consolidadas a las condiciones de esfuerzo efectivo in situ, las cuales se consideran representativas de las condiciones de esfuerzo en el momento de realizar la densificación con explosivos.Resultados: Los resultados de los ensayos triaxiales, realizados bajo condiciones no-drenadas globales, mostraron que, independientemente de la densidad de la muestra, el gas hace que los valores de velocidad de onda de corte obtenidos para las arenas gaseosas se aproximen a los valores de velocidad de onda de corte obtenidos en las muestras saturadas ensayadas bajo condiciones drenadas. Además, este comportamiento tiende a ser más pronunciado a medida que el suelo es más denso. Conclusiones: Esta respuesta podría ofrecer algunas luces sobre porqué la velocidad de corte no se incrementa significantemente en suelos densificados con explosivos aun cuando la densidad se incrementa considerablemente. Palabras clave: arenas sueltas, densificación con explosivos, licuación, mejoramiento de suelos, velocidad de onda de corte Abstract Context: Shear wave velocity tests (Vs) are commonly used to estimate the increase in resistance of explosive densified soils. In some historical cases, Vs tests performed after the soil improvement process Efecto del gas en la velocidad de onda de corte de suelos arenosos densificados con explosivos Effect of gas on shear wave velocity of sandy soils densified with explosives Efecto del gas en la velocidad de onda de corte de suelos arenosos densificados con explosivos Vega-Posada, C.a.; Ramos-Cañón, a.m. y gaRCía-aRistizábal, e.F.

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

Cited by 125 publications

References 20 publications

Mitigation of soil liquefaction using microbially induced desaturation

Mitigation of soil liquefaction using microbially induced desaturation

Centrifuge testing to evaluate the liquefaction response of air-injected partially saturated soils beneath shallow foundations

Efecto del gas en la velocidad de onda de corte de suelos arenosos densificados con explosivos

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