Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions
|Publication Date:||1 November 2011|
This test method covers the determination of the consolidated drained shear strength of one specimen of a soil material under direct shear boundary conditions. The specimen is deformed at a controlled rate on or near a single shear plane determined by the configuration of the apparatus.
Shear stresses and displacements are nonuniformly distributed within the specimen. An appropriate height cannot be defined for calculation of shear strains. Therefore, stress-strain relationships or any associated quantity such as the shear modulus, cannot be determined from this test.
The determination of strength envelopes and the development of criteria to interpret and evaluate test results are left to the engineer or office requesting the test.
The results of the test may be affected by the presence of coarse-grained soil or rock particles, or both.
Test conditions, including normal stress and moisture environment, should be selected to represent the field conditions being investigated. The rate of shearing must be slow enough to ensure drained conditions.
Generally, three or more tests are performed on specimens from one soil sample, each under a different normal load, to determine the effects upon shear resistance and displacement. Results from a test series are combined to determine strength properties such as Mohr strength envelopes. Interpretation of multiple tests requires engineering judgment and is beyond the scope of this test method. This test method pertains to the requirements for a single test.
There may be instances when the gap between the shear box halves should be increased to accommodate sand sized particles greater than the specified gap. Presently there is insufficient information available for specifying the gap dimension based on particle size distribution.
Units-The values stated in either inch-pound units or SI units [given in brackets] are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
The gravitational system of inch-pound units is used. In this system, the pound (lbf) represents a unit of force (weight), while the unit for mass is slugs. The slug unit is not given, unless dynamic (F = ma) calculations are involved.
All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.
The method used to specify how data are collected, calculated, or recorded in this standard is not directly related to the accuracy to which the data can be applied in design or other uses, or both. How one applies the results obtained using this standard is beyond its scope.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
*A Summary of Changes section appears at the end of this standard.