A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering

Thesis (M. Eng.) - Asian Institute of Technology

Cyclic triaxial tests have been carried out on volcanic soil of Lahar sand from erupted materials of mount Pinatubo in Philippines. Liquefaction resistance of this sand is to be urgently investigated since 'super-dike' is planned to be constructed soon using this local sand in the highly seismic area. Samples were reconstituted by two kinds of preparation method, dry deposition and wet tamping, and the range of relative density was between 26% to 80% after isotropically consolidated. Liquefaction resistance or cyclic strength was defined as cyclic stress ratio at 5% double amplitude of axial strain. Samples prepared by wet tamping method exhibit higher cyclic strength than samples prepared by dry deposition. There was a tendency of decreasing cyclic strength when initial effective confining pressure increased, then cyclic strength was determined for 1 kgf/cm2 (98 kPa) confining pressure as a reference. Corrections factor Ka were observed as 1.16 for a' c = 49 kPa and 0. 94 for a' c = 196 kPa. As relative density increased liquefaction resistance became higher. First approximation of relationship between cyclic strength and relative density of Lahar sand was developed for wet tamping and dry deposition method.