Determination of long-term compressive strength of rocks by loading samples with spherical indenters

The article presents the results of experimental studies of the strength properties of rocks during short-term and long-term mechanical tests under uniaxial and volumetric compression. To determine the long-term strength of rocks based on the results of testing samples with spherical indenters, it is proposed to use a traditional approach that takes into account the influence of structural changes in the deformed rock. An accelerated method for determining the limit of long-term strength under uniaxial compression has been developed, based on measuring stresses in a sample at the boundary of an intense fracturing zone near contacts with spherical indenters. The regularities of changes in the long-term strength of rocks under volumetric compression have been investigated. It has been established that the adhesion under volumetric compression and the maximum shear stress differ from similar values in short-term tests to the same extent, determined by the long-term strength coefficient. In this case, the corresponding angles of internal friction in short-term and long-term tests are equal. A calculation method has been developed for determining the long-term strength of rocks under volumetric compression by loading samples with spherical indenters. The method is based on the similarity of structural change processes under short-term and long-term loading conditions in various stress states. The mutual relationship of long-term strength indices under volume compression with compressive strength and brittleness of rocks is studied, on the basis of which dependencies are proposed for calculating long-term strength passport indices under volume compression.

Petrakov D. G., Korshunov V. A., Shokov A. N., Karmanskiy D. A. Determination of long-term compressive strength of rocks by loading samples with spherical indenters. MIAB. Mining Inf. Anal. Bull. 2025;(11-1):38—56. [In Russ]. DOI: 10.25018/0236_1493_2025_111_0_38.

The work was carried out within the framework of the state assignment “Study of thermodynamic processes of the Earth from the position of hydrocarbon genesis at great depths”, FSRW-2024−0008.

Petrakov D. G.¹, Cand. Sci. (Eng.), Vice-Rector for Educational Activities, Petrakov_DG@ pers.spmi.ru, https://orcid.org/0000-0002-0461-1621;
Korshunov V. A.¹, Cand. Sci. (Eng.), Leading Researcher, Korshunov_VA@pers.spmi.ru, https://orcid.org/0009-0002-6330-0230;
Shokov A. N.¹, Cand. Sci. (Eng.), Leading Researcher, Shokov_AN@pers.spmi.ru, https:// orcid.org/0000-0002-0735-2063;
Karmanskiy D. A.¹, Leading Engineer, Karmanskiy_DA@pers.spmi.ru, https://orcid. org/0000-0002-3214-5322.
¹ Empress Catherine II St. Petersburg Mining University, St. Petersburg, Russia.

Korshunov V. A., e-mail: Korshunov_VA@pers.spmi.ru.

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