Advances in Desaturation of Sandy Soil to Mitigate the Liquefaction Hazard-Paper

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The paper reviews soil desaturation as a potentially low-cost, environmentally friendly method for reducing liquefaction risk in loose sandy soils. Conventional approaches—such as vibroflotation, deep dynamic compaction, compaction grouting, and deep soil mixing—can be costly.<br /><br />Desaturation introduces gas into the voids of saturated sand, making the pore-fluid mixture more compressible. During earthquake shaking, this reduces excess pore-water-pressure buildup and increases the soil’s resistance to liquefaction. Research reviewed in the paper uses several methods to create gas or retain air in the soil: air injection, drainage and recharge, electrolysis, and biologically generated nitrogen gas (biogas).<br /><br />Laboratory investigations, including centrifuge, shaking-table, and triaxial tests, generally found that even modest reductions in degree of saturation can substantially improve liquefaction resistance. Desaturated specimens showed lower pore pressures and, in several studies, reduced settlement or greater shear strength. In one shaking-table study, desaturated sand did not liquefy under shaking that liquefied fully saturated sand. Air injection beneath foundations also reduced settlement, although one study observed increased ground acceleration transmitted to the structure.<br /><br />Field trials demonstrated that air can be injected into sandy soil in situ, creating a desaturated zone around the injection borehole. Measurements showed varying degrees of saturation within this zone, and tests on recovered samples confirmed increased liquefaction resistance. Injection pressure must be controlled to avoid disturbing the soil structure.<br /><br />Overall, the reviewed evidence supports desaturation as a promising liquefaction-mitigation technique, while highlighting the need to select and control the method appropriately for site conditions.

Keywords

soil desaturation

liquefaction mitigation

sandy soils

pore pressure

air injection

degree of saturation

earthquake shaking

liquefaction resistance

ground improvement

saturated sand