Linear Variable Differential Transformers (LVDTs), Compressometers, Electrical Resistance Strain Gages). Strain measurement devices: The axial and lateral deformations are measured by various devices (e.g. The length to diameter ratio must also be at least 0.5. Their diameter must be at least equal to the sampleвЂ™s diameter.

Platens: The axial stress applied by the loading device is transferred to the specimen by two steel platens that are made with a minimum Rockwell Hardness of 58. It is pointed out that only strain-controlled devices can capture the post-failure behavior of a material. The test may be stress- or strain-controlled. Loading Device: The loading device must be designed to consistently apply load at the required rate until the end of the test. The apparatus used to conduct the Unconfined Compression Test consists of the following parts: Therefore, moisture recorded in the field should also be preserved until testing.ДЄt least 5 samples are required to achieve a reliable value of the UCS. The purpose of the procedure is to preserve the in-situ properties of the sample until the test is conducted. In particular, the sampleвЂ™s ends must be leveled within a 0.02 millimeters tolerance and they should not depart from perpendicularity by more than 0.06 degrees. The cylindrical surfaces are prepared in order to be flat and smooth. The samplesвЂ™ length to diameter ratio (L/D) must be between 2.0 and 2.5, according to ASTM (American Society for Testing and Materials) and 2.5-3.0 according to ISRM (International Society for Rock Mechanics). The minimum diameter of a specimen must be at least 47 millimeters and 10 times larger than the size of the largest mineral grain (or 6 times larger for weaker rocks e.g.

Samples are retrieved by drill cores and are selected cautiously in order be representative of the original rock formation. On a large scale, the rockmass properties are highly affected by other factors including discontinuities, faults and weathering.Дuring the test, apart from the axial load, axial and lateral deformation are commonly measured to derive the sampleвЂ™s elastic modulus and PoissonвЂ™s ratio. UCS is a parameter widely used in geotechnical design, but may not represent the strength in-situ. Due to the fact that stress is applied along the longitudinal axis, the Unconfined Compression Test is also known as Uniaxial Compression Test. Unconfirmed Compressive Strength (UCS)В stands for the maximum axial compressive stress that a specimen can bear under zero confining stress. The Unconfined Compression Test is a laboratory test used to derive the Unconfirmed Compressive Strength (UCS) of a rock specimen.

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