The direct simple shear test method measures constant volume (undrained) strength and stress-strain characteristics typically of saturated cohesive soils. Following consolidation of the sample (normal stress) a constant rate of shear loading is applied. For a saturated specimen, the constant volume condition allows the shear strength to be measured as if undrained. The strength is then a function of stress conditions, for which the simple shear stress condition can be found below long embankments and many other field situations.

Compared to the direct shear test with a specific horizontal shear plane, direct simple shear generates a fairly equal state of stress throughout the specimen. This can also be an advantageous test when limited soil is available.