Triaxial compression tests

Specimens from drill cores are prepared by cutting them to the specified length and are thereafter grinded and measured. There are high requirements on the flatness of the endsurfaces in order to obtain an even load distribution. Recommended ratio of height/diameter of the specimens is between 2 and 3.


A membrane is mounted on the envelope surface of the specimen in order to seal the specimen from the surrounding pressure media. Deformation measurement equipment are mounded on the specimen and the specimen is inserted into the pressure cell whereupon the cell is closed and filled with oil. A hydrostatic pressure is applied in the first step. The specimen is then further loaded by increasing the axial load under constant or increasing cell pressure up to failure or any other pre-defined load level.

 - Cell pressure up to 100 MPa
 - Air-hole pressure up to 100 MPa
 - Breaking stress
 - Angle of friction
 - Parameter of elasticity: E, ν
 - Post-failure



Stress state and deformations during the test. 



Specimen inserted in between the loading platens, with equipment for deformation measurement attached on the specimen, before the cell is closed.

The pictures below show a specimen which has a shear failure.


The results and pictures are taken from

Jacobsson, L. Oskarshamn site investigation, Borehole KLX03A, Triaxial compression test of intact rock. SKB-P05-96, Svensk Kärnbränslehantering AB, 2005.

This and many other reports on triaxial compression tests, conducted at SP, are published on SKB

Example of standards

ISRM 1978, Suggested methods for determining the strength of rock materials in triaxial compression. Int J Rock Mech Min Sci Geomech Abs 15(3, sid 99-103.

Related Information


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Experimental Resources

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See also

SKBDokumentet öppnas i ett nytt fönster

Contact Persons

Lars Jacobsson

Phone: +46 10 516 56 19

Mathias Flansbjer

Phone: +46 10 516 52 25

RISE Research Institutes of Sweden, Phone 010-516 50 00, E-mail

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