Figure 1. Machine with mounted specimen that uses in UCS test

The sample is fallen under increasing axial load with constant rate. The axial load and time is fixed during testing. If uniaxial compressive strength alone is required the load will be noted. Next step is determination cross-section area of the sample named A. Then uniaxial compressive strength can be obtained from next equation:

(1)

From this test it can possible to take only one failure point. Other points are needed if a strength criterion is required [1]. Also this test can be used for determination of porosity because of relationship with ambient porosity.

Results of test with several samples are represented on Figure 2. The relationship between axial displacement and axial load should be linear for perfectly elastic material and the slop of this line is equal to modulus of elasticity. But there is no perfectly elastic rock in reality. Because of this tested relationship have curve shape. This shape depends on conditions of testing. That is why it is better that results will be qualified by quoting test conditions [1]. The calculation uniaxial compressive strength is represented at the table 1.

№ of samples	R, m	Area,	Maximum of , N	, Mpa
R1	0.019	0.0011335	14531.25	12.819
R2	12187.5	10.752
W1	68906.25	60.789
W2		102.555

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