Cyclic response and liquefaction resistance due to de-saturation of sand

Juneja, A., and Raghunandan, M.E. (2011)., Proceedings of 14th Asian Regional Conference on Soil Mechanics & Geotechnical Engineering (14ARC), Hong Kong, China, 310 (full paper on CD). (SCOPUS), 2011

It is well known that the presence of air pockets in saturated sand increase its shear strength as well as the resistance to liquefaction. This paper discusses the results of strain controlled cyclic triaxial tests conducted on  sands in which air pockets were pre-introduced prior to start of the undrained cyclic shear. The results indicate that when the degree of saturation was reduced only slightly, there was considerable in-crease in the number of cycles required to induce liquefaction. Also proposed in this paper is modulus in-crement ratio, Gr defined as the ratio of the shear modulus of de-saturated sample to the shear modulus of the saturated sample measured at equal shear strains. Gr was shown to approach unity at shear strains less than 0.001 and more than 0.011. In between the two limits, Gr was found to reach a transient peak for the entire range of degree of saturation investigated in this study.