Air injection to mitigate liquefaction under light structures

During large earthquakes, soil liquefaction has repeatedly damaged many buildings with shallow foundations. Many researchers have continuously worked to develop more reliable countermeasure techniques apposite to the foundation soils of existing buildings. However, most countermeasure techniques available in the current practice are either too expensive or applicable only to new construction sites. Lowering the degree of saturation by artificially injecting air is a newly developed, innovative technique that significantly improves the liquefaction strength of soil. This paper describes a series of centrifuge tests for evaluating the effectiveness of this technique by applying it to the foundation soil underlying shallow foundations of relatively light structures, such as residential buildings. Models of saturated medium dense sand beds with shallow foundations were shaken in a centrifuge. Except for benchmark models, air was injected into the soil in-flight before the shaking event, which lowered the degree of saturation of the soil in the desaturated zone from 100% before air injection to approximately 85%. The test results show that air injection effectively reduced both foundation settlement and pore pressures generated below the foundation.