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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
A soil test is a laboratory or in-situ analysis to determine the chemical, ... An example soil sample report is provided for reference by Wallace ... Direct shear test;
Direct shear test ASTM D3080. The direct shear test determines the consolidated, drained strength properties of a sample. A constant strain rate is applied to a single shear plane under a normal load, and the load response is measured. If this test is performed with different normal loads, the common shear strength parameters can be determined ...
Triaxial apparatus with sample attached ready for testing. In materials science, a triaxial shear test is a common method to measure the mechanical properties of many deformable solids, especially soil (e.g., sand, clay) and rock, and other granular materials or powders.
This strict definition of the steady state was used to describe soil shear as a dynamical system (Joseph 2012). Dynamical systems are ubiquitous in nature (the Great Red Spot on Jupiter is one example) and mathematicians have extensively studied such systems. The underlying basis of the soil shear dynamical system is simple friction (Joseph 2017).
Dilatancy of a sample of dense sand in simple shear. The phenomenon of dilatancy can be observed in a drained simple shear test on a sample of dense sand. In the initial stage of deformation, the volumetric strain decreases as the shear strain increases. But as the stress approaches its peak value, the volumetric strain starts to increase.
The output of the analysis is a factor of safety, defined as the ratio of the shear strength (or, alternatively, an equivalent measure of shear resistance or capacity) to the shear stress (or other equivalent measure) required for equilibrium. If the value of factor of safety is less than 1.0, the slope is unstable.
Only for simple models of discontinuities the shear strength can be analytically calculated. [8] For real discontinuities no analytical calculation method exists. Testing on various scales in the laboratory or in the field, or empirical calculations based on characterizing the discontinuity [12] [14] [15] are used to establish the shear strength.