Laboratory tests were performed to investigate the liquefaction susceptibility of uncemented calcareous sands. A series of isotropically consolidated undrained monotonic and cyclic triaxial tests were performed using the Playa Santa sand from Porto Rico. Playa Santa sand is a poorly graded calcareous clean beach sand composed of angular particles with large intra-granular voids. A series of consolidated undrained triaxial tests were performed with the Playa Santa sand remolded to a variety of relative densities and consolidated under a range of confining pressures. In addition, cyclic triaxial tests were performed at a confining pressure of 100 kPa and three sets of relative densities (20%, 40% and 60%). Generation of excess pore pressure under different levels of cyclic loading was established. As a result, relationships were developed to relate the number of cycles required for triggering of liquefaction to cyclic stress ratio. It was seen that the Playa Santa sand was less susceptible liquefaction than quartzitic sands of the same relative density remolded and tested under similar conditions. / Master of Science