Loading
Nota de Estudos
Study Reminders
Support
Text Version

Shear Strength Measurement - Lesson Summary

Set your study reminders

We will email you at these times to remind you to study.
  • Monday

    -

    7am

    +

    Tuesday

    -

    7am

    +

    Wednesday

    -

    7am

    +

    Thursday

    -

    7am

    +

    Friday

    -

    7am

    +

    Saturday

    -

    7am

    +

    Sunday

    -

    7am

    +

Shear Strength of Unsaturated Soils - Concepts
In order for soils to support foundations or structures, the shear strength of the soil should be sufficient to withstand any load condition. Coulomb established friction laws that established the understanding of the shear strength of soils. He looked at soil as a single-phase system. He proposed that the shear stress of soil is proportional to its total stress. Terzaghi, in 1920, looked at soils as a two-phase system. He introduced the concept of effective stress, in order to help understand soil behaviour and the influence of drainage conditions. In 1959, a British man called Bishop came up with the idea of how the behaviours of unsaturated soils can be predicted using the concept of negative pore water pressure.
Suction-Controlled Direct Shear Test
According to Bishop, unsaturated strength parameters can be analysed by considering two independent trusted variables, such as net normal stress and matrix suction. The two independent trusted parameters are lumped into one single equation for defining the effective stress equation.
The effective stress parameter for an unsaturated soil can be estimated from the experimental data that are obtained from a Suction-Controlled Direct Shear Test. With the introduction of the effective stress principle in Modified Mohr-Coulomb concept, the effective stress parameter can be obtained.
Suction-Controlled Triaxial Test
Generally, in Triaxial test, the data from deviatoric stress is used. The deviatoric stress is dependent on the type of test. It is simply shear stress versus axial strain. The major limitation of the Bishop's Effective Stress Model is that it requires so many number of tests to be conducted at different suction values.