Search results
Results from the WOW.Com Content Network
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.
Cohesion is the component of shear strength of a rock or soil that is independent of interparticle friction. In soils, true cohesion is caused by following: Electrostatic forces in stiff overconsolidated clays (which may be lost through weathering) Cementing by Fe 2 O 3, Ca CO 3, Na Cl, etc. There can also be apparent cohesion. This is caused by:
Different criteria can be used to define the "shear strength" and the "yield point" for a soil element from a stress–strain curve. One may define the peak shear strength as the peak of a stress–strain curve, or the shear strength at critical state as the value after large strains when the shear resistance levels off.
It is useful to know the range of expected values depending on the type of soil being analyzed. For example, in samples with natural moisture content at the liquid limit (liquidity index of 1), preconsolidation ranges between about 0.1 and 0.8 tsf, depending on soil sensitivity (defined as the ratio of undisturbed peak undrained shear strength ...
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.
A direct shear test is a laboratory or field test used by geotechnical engineers to measure the shear strength properties of soil [1] [2] or rock [2] material, or of discontinuities in soil or rock masses. [2] [3] The U.S. and U.K. standards defining how the test should be performed are ASTM D 3080, AASHTO T236 and BS 1377-7:1990, respectively.
The values of these limits are used in several ways. There is also a close relationship between the limits and properties of soil, such as compressibility , permeability , and strength . This is thought to be very useful because as limit determination is relatively simple, it is more difficult to determine these other properties.
Most of the classical engineering materials follow this rule in at least a portion of their shear failure envelope. Generally the theory applies to materials for which the compressive strength far exceeds the tensile strength. [1] In geotechnical engineering it is used to define shear strength of soils and rocks at different effective stresses.