Shear Behavior: Short-Term and Long-Term

Reminder

Soils consist of three phases: solid, liquid, and gas. It is essential to distinguish between effective stresses and total stresses.

Definition

Granular Soil with high permeability allows rapid drainage under external loads. Shear behavior and strength are governed by the solid skeleton.

Fine Soils: with low permeability results in slow drainage. Two extreme behaviors are observed:

  • Short-Term Behavior: Undrained conditions, where water plays a significant role in mechanical behavior.

  • Long-Term Behavior: Drained conditions, where pore water pressures dissipate, and behavior is governed by the solid skeleton.

Drained and undrained conditions

Several types of tests are used to determine the plasticity characteristics; these include:

In-situ measurement tests (vane shear test, penetrometer, etc.),

Laboratory tests (unconfined compression test, direct shear test or Casagrande shear box, triaxial compression test).