Employing soil improvement techniques to mitigate and prevent the detrimental effects of liquefaction on foundations often leads to a significant increase in construction costs in engineering projects. Developing simple, cost-effective, and eco-friendly liquefaction mitigation methods has always been one of the main concerns of geotechnical engineers. Researchers introduced the induced partial saturation (IPS) method to increase the liquefaction resistance of the saturated foundations, which is based on decreasing the saturation degree of the saturated sand. In this study, hollow cylinder torsional shear tests were conducted on loose saturated and desaturated calcareous sand to assess the liquefaction behavior of desaturated sand. Soil compressibility is the primary parameter affecting the liquefaction behavior of desaturated sand. As saturation degree, back pressure, and effective confining pressure significantly influence soil compressibility, their effects on the liquefaction resistance of desaturated sand were investigated. The pore pressure development during cyclic loading reveal that, unlike saturated samples, desaturated samples do not exhibit an excess pore pressure ratio reaching one, even when the double amplitude shear strain surpasses 7.5 %. Finally, the test results demonstrated a notable correlation between liquefaction resistance ratio, maximum volumetric strain, and the maximum generated excess pore pressure ratio, and a pore pressure model was proposed.

As a cost-effective and environmentally friendly technique for enhancing the liquefaction resistance of sandy soils, the air-injection method has attained widespread application in multiple soil improvement or desaturation strategies. This study reports undrained cyclic loading experiments on reconstituted, slightly desaturated sand specimens under either isotropic or anisotropic consolidation to examine the effects of the presence of injected air and initial stress anisotropy on the energy-based assessment of pore pressure and liquefaction resistance. The results exhibited three different cyclic response patterns for the saturated/desaturated specimens with distinct deformation mechanisms, revealing that the sand has a higher degree of stress anisotropy and lower degree of saturation typically being more dilative and less susceptible to cyclic liquefaction. The energy-based liquefaction potential evaluation indicates that the accumulative energy is mathematically correlated with the pore pressure, thus establishing a unified energy-pore pressure relationship for both saturated and desaturated sand. Furthermore, the energy capacity for triggering cyclic failure demonstrates a consistently rising trend with an increase in the consolidation stress ratio and a reduction in the degree of saturation, which seems closely linked to the cyclic liquefaction resistance. This result signifies the potential applicability of an energy-based approach to quantify the liquefaction susceptibility of desaturated in situ soils using strength data from conventional stress-based analyses.