The Unconfined Compression Test is a laboratory test used to derive the Unconfirmed Compressive Strength (UCS) of a rock specimen. Unconfirmed Compressive Strength (UCS) stands for the maximum axial compressive stress that a specimen can bear under zero confining stress. Due to the fact that stress is applied along the longitudinal axis, the Unconfined Compression Test is also known as Uniaxial Compression Test. UCS is a parameter widely used in geotechnical design, but may not represent the strength in-situ. On a large scale, the rockmass properties are highly affected by other factors including discontinuities, faults and weathering.

During the test, apart from the axial load, axial and lateral deformation are commonly measured to derive the sample’s elastic modulus and Poisson’s ratio.