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  • 1
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    Cracking in drying soils (1992)
    Canadian Science Publishing
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    Publication Date: 1992-04-01
    Description: Cracking in soils that are undergoing drying is controlled by soil suctions and by soil properties such as compression modulus, Poisson's ratio, shear strength, tensile strength, and specific surface energy. The paper reviews the occurrence and morphology of cracks in dry-climate regions of Australia and Canada. After reviewing the behaviour of unsaturated soils and the mechanics of cracking, solutions are developed based on (i) elasticity theory, (ii) the transition between tensile and shear failure, and (iii) linear elastic fracture mechanics. The solutions are compared and related to crack depths observed in the field. Key words : clay, cracks, crust, shear strength, soil suction, tensile strength, unsaturated soil, weathering.
    Print ISSN: 0008-3674
    Electronic ISSN: 1208-6010
    Topics: Geosciences
    Published by Canadian Science Publishing
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  • 2
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    A numerical study of steady state evaporative conditions applied to mine tailings (1999)
    Canadian Science Publishing
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    Publication Date: 1999-11-22
    Description: The suction profile of a desiccating soil is dependent on the water table depth, the soil-water retention characteristics, and the climatic conditions. In this paper, an unsaturated flow model, which simulates both liquid and vapour flow, was used to investigate the effects of varying the water table depth and the evaporation rate on the evaporative fluxes from a desiccating tailings deposit under steady-state conditions. Results obtained showed that at a critical evaporation rate, beyond which evaporation is no longer dictated by climatic conditions, the matric suction profiles remain basically unchanged. The critical evaporation rate varies inversely with the water table depth. It is associated with the maximum evaporative flux that might be extracted from a soil at steady-state conditions. The time required to establish steady-state conditions is directly proportional to the water table depth, and it acquires a maximum value at the critical evaporation rate. A detailed investigation of the movement of the drying front demonstrated the significance of attaining a matric suction of about 3000 kPa on the contribution to flow in the vapour phase.Key words: matric suction, mine tailings, potential evaporation, steady state evaporative conditions, surface evaporative flux.
    Print ISSN: 0008-3674
    Electronic ISSN: 1208-6010
    Topics: Geosciences
    Published by Canadian Science Publishing
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  • 3
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    Search for critical slip surfaces based on finite element method (1995)
    Canadian Science Publishing
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    Publication Date: 1995-04-01
    Description: In this paper, finite element methods (FEM) are used to determine local shear strength mobilization ratios within a slope and to indicate the probable location of the critical slip surface. To locate the critical slip surface and hence determine the minimum factor of safety, an improved dynamic programming method (IDPM) is employed, in which possible slip surfaces, which must pass between state points, may pass both between and along stages. The IDPM is coupled with an expression for the factor of safety for which the stresses are obtained from the FEM. The results obtained using the FEM–IDPM, for a homogeneous slope and for a test embankment on soft Bangkok clay, have been compared with those observed and obtained using the traditional finite element method and the generalized limit equilibrium wedge method. The FEM–IDPM has the advantage over limit equilibrium methods that the strain- and time-dependent behaviour of soil and the staged construction of the slope can be modelled. Key words : critical slip surface, dynamic programming, factor of safety, finite element method, limit equilibrium method, slope stability.
    Print ISSN: 0008-3674
    Electronic ISSN: 1208-6010
    Topics: Geosciences
    Published by Canadian Science Publishing
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  • 4
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    A relationship describing the shear strength of unsaturated soils (1999)
    Canadian Science Publishing
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    Publication Date: 1999-09-25
    Description: A relationship describing the shear-strength profile of a desiccating soil deposit is essential for the purpose of analysis, especially when a numerical method is adopted where each zone in a discretised grid is assigned an elevation-dependent shear-strength value. The matric-suction profile of a desiccating soil deposit is nonlinear. Up to the air-entry value, an increase in matric suction is associated with a linear increase in shear strength. Beyond air entry, as the soil starts to desaturate, a nonlinear increase in shear strength occurs. The soil-water characteristic curve is stress dependent, as is the shear-strength gain as matric suction increases. In this paper, a three-dimensional, nonlinear regression analysis showed that a power-additive function is suitable to describe the variation of the shear strength of unsaturated soils with matric suction. The proposed function incorporates the effect of normal stress on the contribution of matric suction to the shear strength.Key words: air-entry value, matric suction, nonlinear regression, soil-water characteristic curve, tailings, unsaturated shear strength.
    Print ISSN: 0008-3674
    Electronic ISSN: 1208-6010
    Topics: Geosciences
    Published by Canadian Science Publishing
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  • 5
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    Effective stress vane shear strength correction factor correlations (1994)
    Canadian Science Publishing
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    Publication Date: 1994-06-01
    Description: A recent effective stress model of vane shear strength testing in soils can relate measured torques to vane shear strengths using theoretical analysis in terms of effective stress parameters. The strength estimates are based on known in situ stresses and soil parameters derived from laboratory testing. The model may be applied, for example, in obtaining theoretical estimates of conventional undrained vane shear strengths for comparison with field data and for use in stability analyses. However, the model incorporates a correction factor μv, analogous to Bjerrum's field vane shear strength correction factor μ, intended to compensate for pore-pressure and shearing-rate effects. This correction factor must be evaluated before reliable torque or shear strength estimates can be made in any given case. To facilitate this, the paper presents correlations of μv with both liquid limit and plasticity index, based on world-wide data from clays and silts. The correlations are compared with independent data from Norwegian clays. Key words : clay, correction factor, effective stress, liquid limit, plasticity index, silt, vane shear strength.
    Print ISSN: 0008-3674
    Electronic ISSN: 1208-6010
    Topics: Geosciences
    Published by Canadian Science Publishing
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