Slurry Deposition Method of Low-Plasticity Intermediate Soils for Laboratory Element Testing

A repeatable preparation method is useful for investigating systematic variations in behavior across a range of soil types (e.g., gradation, plasticity) and test conditions (e.g., stress level, stress history). Existing methods for preparation of laboratory specimens can be generally categorized into those for cohesionless and cohesive soils, thereby focusing on a narrow range of soils and test conditions. The applicability of these conventional preparation techniques for soils with intermediate (or transitional) properties and behaviors are relatively unknown. In this study, a range of intermediate soils that are not amenable to traditional sand-like or claylike characterization are prepared using a slurry deposition technique and evaluated in oedemetric consolidation, undrained monotonic triaxial shear, and both undrained monotonic and undrained cyclic direct simple shear by three researchers at two separate universities. Results indicate that the slurry technique developed herein can produce uniform mixtures of nonplastic, low-plasticity, and high-plasticity soils, with repeatable behaviors obtained from singular mixtures for all test methods. Evaluation of specimen response across this range of soils exhibits systematic trends of increasing compressibility with increasing plasticity and a transition from dilative to contractive tendencies with increasing soil plasticity. Collectively, these results for synthetic mixtures of silica silt and kaolin clay suggest that the slurry deposition technique is applicable to fine-grained, intermediate soils across a range of plasticity from nonplastic to high-plasticity soils.