Unconfined compressive strength

UCS (also frequently named C0)Critical stress value at which a rock body fails brittlely under compresion. It may be determined directly via a uniaxial test under unconfined compressive conditions (σ1>>σ23=0 MPa) or by a series of triaxial tests (σ123≠0 MPa). In the latter case it is necessary to determine peak strength at several confining pressure stages (either via various single stage tests or via one multi stage experiment) and to draw a regression line through all peak strength data points to unravel the peak strength at 0 MPa as the UCS. This indirect way to determine UCS yields higher stress values than the direct measurements due to the fact that during confining pressure buildup in triaxial deformation tests microfractures are closing which will remain open during an unconfined compressive test. Consequently, only indirect UCS determination gives data for intact rock and only those data can be used for comparison with other data for the same rock type. Rock UCS values roughly range from 1 MPa (weakly consolidated sandstone) to 350 MPa (granite and basalt).

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05.05.2025 · DGMK Spring conference 2025

DGMK/ÖGEW spring conference 2025 goes on tour and we are part of it!

Meet us on booth 2, we look forward to a lively exchange in Papenburg.

 

03.10.2024 · Project HENRI

Gesteinslabor Dr. Eberhard Jahns is project and research partner within the HENRI (Hydrogen Energy Reservoir) project.

Main focus of us is the impact of H2 on the cap rock. Besides other parameters, we determine the capillary threshold pressure with different gases and gas mixtures.

First preliminary results could be presented at the 2nd HENRI conference.

 

28.07.2023 · Find us in EEK

Recently, the article "Determination of capillary threshold pressure with hydrogen gas" was published in the journal EEK.
Article from the journal EEK 01/2023

01.12.2022 · 

Gesteinslabor has successfully completed the development of a new test rig to determine the capillary threshold pressure with hydrogen.