| Grain shape is a fundamental property of sedimentary particles that effects geologic and engineering behavior of particles and particle masses. Grain shape measurement is important to sedimentary geologic and engineering research into behavior of granular masses. In geologic and engineering research there has not been a rapid, precise and mathematically-based grain shape measurement method. This study investigated the influence of grain shape and surface texture on the shear strength of cohesionless materials.;The research program consisted of sample preparation, measurement of physical properties, grain shape measurement using Fourier analysis, scanning electron microscopy, and direct shear tests. Glass ballotini, St. Peter Sandstone, Antietam Quartzite and calcite sand were selected for this study to represent a range in surface texture and be similar in other physical properties.;The Rittenhouse scale of sphericity and Krumbein roundness chart were analysed with the Fourier method. The resulting data were analysed using linear regression to establish a correlation between shape features and Fourier measurements. Correlation equations derived from the charts were used to calculate a Rittenhouse sphericity value (R;Twenty-nine direct shear tests were conducted at normal stresses of about 2, 5 and 10 pounds per square inch. Direct shear test results were plotted on stress-strain curves and maximum shear stress values identified. Shear stress versus normal stress was plotted to derive shear strength envelopes. Angles of shearing resistance were then derived using linear regression.;The primary influence of surface texture on shear strength of granular materials is in interparticle movement and development of resistance to shear. The results of this study indicate that shear strength increases with increasing surface texture or surface roughness. Difficulty in handling during testing also increases with increasing surface texture. Before Fourier grain shape analysis can be used to predict material behavior, additional research is needed to evaluate shear strength of materials with varying grain shapes and surface textures, and gradational mixes. |
