Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A direct shear test is a laboratory test used by geotechnical engineers to find the shear strength parameters of soil. In the U.S., the standard defining how the test should be performed is ASTM D 3080. The test is performed on three or four specimens from a relatively undisturbed soil sample. A specimen is placed in a shear box which has two stacked rings to hold the sample; the contact between the two rings is at approximately the mid- height of the sample. A confining stress is applied vertically to the specimen, and the upper ring is pulled laterally until the sample fails, or through a specified strain. The load applied and the strain induced is recorded at frequent intervals to determine a stress-strain curve for the confining stress. Direct Shear tests can be performed under several conditions.