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The shear strength of soil depends on the effective stress, the drainage conditions, the density of the particles, the rate of strain, and the direction of the strain. For undrained, constant volume shearing, the Tresca theory may be used to predict the shear strength, but for drained conditions, the Mohr–Coulomb theory may be used.
In a 'consolidated undrained' test, the sample is not allowed to drain. The shear characteristics are measured under undrained conditions, and the sample is assumed to be fully saturated. Measuring the pore pressures in the sample (sometimes called CUpp) allows for approximating the consolidated-drained strength.
The test using the direct shear machine determines the consolidated drained shear strength of a soil material in direct shear. [4] The advantages of the direct shear test [5] over other shear tests are the simplicity of setup and equipment used, and the ability to test under differing saturation, drainage, and consolidation conditions. These ...
If the rate of shearing is very large compared to the rate that water can be sucked into or squeezed out of the dilating or contracting pore spaces, then the shearing is called undrained shear, if the shearing is slow enough that the water pressures are negligible, the shearing is called drained shear. During undrained shear, the water pressure ...
The gauge is marked with a scale that converts the torque into a shear strength (measured in kiloNewtons per square metre). There are two scales for use with two different sizes of vane – 150-by-75-millimetre (5.9 in × 3.0 in) vanes are used for soils with shear strengths up to 50 kN/m 2 and 100-by-50-millimetre (3.9 in × 2.0 in) vanes for ...
Consequently, models based on a metals based theory of plasticity are not able to model behavior of soils that is a result of anisotropic particle properties, one example of which is the drop in shear strengths post peak strength, i.e., strain-softening behavior.
The shearing strength of clay at the plastic limit is a measure of its toughness. It is the ratio of the plasticity index to the flow index. It gives us an idea of the shear strength of the soil.
Other advantages of the fall cone test include the alternative to estimate the undrained shear strength of a soil based on the fall cone factor K. [2] In the Fall cone test, a stainless steel cone of a standardized weight and tip angle is positioned so that its tip just touches a soil sample. The cone is released for a determined period of time ...