Abstract
Desaturation is a new method to mitigate liquefaction of sand. It aims to prevent liquefaction by generating gas/air in the pores of fully saturated sands, and biogas is one of the most suitable gas. In order to evaluate the long-term sustainability of biogas bubbles, a series sustainability test on biogas bubbles in pores of sand was conducted with a one-dimensional device under hydrostatic condition, hydraulic gradient flow condition and horizontal excitation condition. The variation trend of the retention of biogas bubbles in the pores of soil under the aforementioned conditions was analyzed. Test results indicated that after 72 weeks of monitoring sand samples, biogas bubbles existed stably in the pores of soil under hydrostatic conditions. In hydraulic gradient flow, the stability under upward seepage flow showed a similar trend to that of downward seepage flow. When the hydraulic gradient was constant, the degree of saturation increased in a certain period and finally remained constant. When the hydraulic gradient increased by 0.1, 0.2, 0.3, 0.4, and 0.5, the degrees of saturation increase were 0.8%, 11.5%, 0.5%, 0.1%, and 0%, respectively. After 41,200 cycles with different accelerations, the degree of saturation of the sample increased slightly, and the biogas bubbles basically remained stable.
Highlights
Desaturation is a new method to mitigate liquefaction of sand
Yegian et al.[33] prepared unsaturated samples that contained air bubbles by drainage–recharge, after 442 days, the degree of saturation increased from 82.1% to 83.9%, which indicated a 1.8% increase
According to the above test results, nitrogen bubbles produced by microorganisms are more stable than air bubbles
Summary
Desaturation is a new method to mitigate liquefaction of sand. It aims to prevent liquefaction by generating gas/air in the pores of fully saturated sands, and biogas is one of the most suitable gas. Yegian and Eseller proposed a method of using electrolytic water to produce hydrogen and o xygen[28] in saturated soil to reduce its saturation and thereby improve the anti-liquefaction strength of soil[22]. He et al.[29] studied the stability of biogas bubbles under seepage conditions by using a one-dimensional model sand column and found that some bubbles would flow out together with pore water under seepage conditions and reduce the degree of saturation effect. The results can reflect the effective time of a single reinforcement using biogas bubbles, which provide a theoretical basis for application of the construction using desaturation method
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