ABSTRACT Calcareous sands often consist of skeletal remains of marine organisms. Intraparticle voids exist in such sands. These tend to crush more readily under stress than terrigeneous sands. This paper presents laboratory triaxial test data for low and elevated cell pressures up to 64 kgfcm2 for four calcareous sands from the west coast of India. The extent of crushing is expressed through a dimensionless crushing coefficient. Of the four sands investigated, one consisted of coralline debris; others were mixes of coralline debris, shell fragments, and other skeletal remains. Investigations revealed that crushing increases with increasing confinement, application of shear stress, increasing abundance of intraparticle voids and plate-like shell fragments, increasing angularity of particles, and increasing size of particles. As crushing increases, the deviator stress-axial strain behavior changes from brittle type to plastic type and the volume change during shear alters from dilatant to one of volume reduction. A normalized parameter reflecting the decrease in the maximum principal effective stress ratio was found to be a unique function of the crushing coefficient for the four sands investigated. INTRODUCTION Sands are known to crush under stresses at high confinement. Particle crushing is more predominant under shear stresses than under isotropic compression. Stresses in soil under deep foundations often reach the range where crushing becomes significant. Calcareous sands crush more readily than terrigeneous sands. Calcareous sands occur as skeletal remains of marine organisms and/or as nonskeletal oolites of calcareous material. Skeletal calcareous sand grains are characterized by the presence of intraparticle voids that increase the tendency of these sands to crush under stress. Presence of thin plate-like shell fragments further increases the crushability of calcareous sands. The behavior of calcareous sands has been observed to be markedly different from the terrigeneous sands. Static pile load tests in calcareous sand strata have yielded very low skin friction values.1,2 Piles driven in calcareous sand also have been found to encounter low driving resistance.8 Both these peculiar phenomena have been attributed to particle crushing. This paper describes results of an experimental investigation designed to determine the amount of crushing in calcareous sands under low and elevated cell pressures and assesses the influence of crushing on the shear characteristics of such sands and, thus, in part offers an explanation to the low skin friction values encountered in the field tests. QUANTITATIVE EXPRESSION FOR DEJREE OF CRUSHING Different methods of quantitatively expressing the degree of crushing have been proposed by various investigators. Lee and Farhoomand5 studied crushing of material under anisotropic compression and have defined a parameter that they designated as relative crushing, which is equal to D15i/D15a, where D15i is the diameter through which 15% of particles of the original material pass and D15a/ is the diameter through which 15% of the particles pass after being subjected to anisotropic compression. Ramamurthy and Lal have expressed quantitatively the degree of crushing as the area between the grading curves of a sand obtained before and after it has been subjected to shear.