1.1 This test method is designed to assess the consolidated drained shear strength of a soil material sample under direct shear conditions. The sample is subjected to deformation at a consistent rate, typically on or close to a single shear plane that is determined by the setup of the testing apparatus.

1.2 Within the specimen, shear stresses and displacements are not evenly distributed. As a result, a precise failure zone height cannot be established for calculating shear strains, and therefore, stress-strain relationships or related parameters like the shear modulus cannot be derived from the test.

1.3 The test results can be compromised by the presence of coarse-grained soil or rock particles, or a combination of both, which may render the testing data unreliable in certain instances. Refer to the requirements for maximum soil particle size in sections 6.2.1 and 6.2.2.

1.4 The test conditions, including the normal stress, access to water during consolidation and shearing, and the state of the specimens, should be chosen to reflect the field conditions under investigation, and this decision is at the discretion of the engineer or the entity requesting the test. The shearing rate must be slow to ensure that drained conditions are maintained.

1.5 Typically, three or more tests are conducted on samples from a single soil batch, each at a different normal load, to investigate the impact on shear resistance and displacement. The establishment of criteria for interpreting and evaluating these test results is the responsibility of the engineer or the requesting office. The interpretation of multiple tests requires engineering expertise and falls outside the scope of this test method, which focuses on the requirements for a single test.

1.6 This test method sets a maximum particle size limit for the test specimen based on the dimensions of the shear box. Additionally, the gap size during shearing is specified. It is permissible for the test requestor to specify a particular gap size between the upper and lower halves of the shear box to accommodate certain sand size particles. Currently, there is not enough information to establish a gap dimension based on the particle size distribution.