Influence of Particle Softness and Damage on Engineering Behaviour of Granular Soils

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Soft sand particles (e.g. carbonates) deform due to high stress at particle contacts and lead to increased volumetric contraction, strain-softening and liquefaction failure. Particle damage and crushing, occurring beneath foundations, high embankments, pile driving, in-situ tests, large run-out landslides, and earthquakes, also contribute to sand compressibility and susceptibility to shear failure. However, the role of these particle compression mechanisms in the behaviour of sands and other granular soils, and in the interpretation of laboratory and in-situ field tests is not yet well understood, which has led to unexpected geotechnical hazards. Therefore, in addition to soil structure (i.e. fines content, and density), soil particle compressibility needs to be properly characterized. In the proposed research, the influence of sand particle compressibility mechanisms on its behaviour will be studied through: (a) micro-scale discrete element modeling, (b) laboratory element-scale testing, and (c) macro-scale field tests. The influence of these compressibility mechanisms will be integrated in soil constitutive models and advanced numerical analysis used in Canadian practice. In-situ field test results will be collected from geotechnical engineering literature survey and industry to develop an empirical relationship for predicting in-situ field test response from the behaviour and state of compressible sands. A new correction factor will be developed to correct field test results in compressible sands, and thus use the wide range of interpretations available for low-compressibility sands. This correction factor will be implemented in geotechnical design guidelines in Canada to achieve safer and more economical design of slopes, foundations, and earthquake remediation techniques, and prevent unexpected catastrophic landslides and failures. No Canadian guideline or commentary currently provides any guidance on the influence of particle softness, and crushing for practice. The proposed research program will train 2 undergraduate, 2 MESc, and 3 PhD students.