Cyclic shear response of undisturbed and reconstituted Fraser River Silt

Maria V. Sanín, Dharma Wijewickreme

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Laboratory Testing

ABSTRACT: The cyclic shear response of natural low-plastic Fraser River silt was investigated under constant volume direct simple shear loading using specimens from undisturbed samples and by reconstitution of the same material. During monotonic shear loading, the reconstituted specimens exhibited a generally weaker stress-strain response compared to those displayed by the undisturbed specimens. The results of the cyclic tests also demonstrate that the specimens of undisturbed silt, despite having a looser density under identical consolidation stress conditions, exhibited more dilative response and larger shear resistance compared to those displayed by reconstituted specimens. These observed differences between the undisturbed and reconstituted materials suggest that commonly used state variables e and sv alone are not sufficient to determine the shear behaviour of low plasticity silt. The differences in the behaviour can be attributed to the difference in particle structure (soil fabric) between the undisturbed and reconstituted specimens. PRESENTACIONES TÉCNICAS La respuesta de limos de baja plasticidad provenientes del Río Fraser fué investigada en pruebas de corte simple directo a volúmen constante usando muestras inalteradas y reconstituidas del mismo material. Durante las pruebas monotónicas, los especímines reconstituidos presentaron una relación esfuerzo-deformación más baja que la de las muestras inalteradas.. Los resultados de las pruebas cíclicas también mostraron que las muestras inalteradas, a pesar de tener una densidad más baja a condiciones similares de consolidación, presentaron una respuesta más dilatante y una resistencia cíclica mayor comparada con la de los expecímes reconstituídos. Estas diferencias sugieren que las variables de estado comunmente usadas e y sv, no son suficientes para determinar la respuesta de limos de baja plasticidad. El contraste en la respuesta puede ser atribuido a las diferencias en la estructura de las partículas (textura) entre los especímenes inalterados y reconstituídos.

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