The Brazilian tensile strength as an alternative for point load index in the Rock Mass Rating system

Articles in Press

Document Type : Research Paper

Authors

1 Department of Geology, Faculty of Basic Sciences, Lorestan University, Khorramabad, Iran

2 Department of Geology and Pole of Geosciences Center, University of Trás-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal

3 Damghan University, School of Earth Sciences, Damghan, Semnan, Iran

Abstract

The Rock Mass Rating (RMR) system is widely used to assess rock mass quality and the its mechanical parameters including cohesion, internal friction angle, and elasticity modulus. The uniaxial compressive strength (UCS)/point load index (PLI) of intact rock is one of the input parameters in RMR. Rocks in some geotechnical works, such as rock slopes, tunnels, and some foundations are under tensional stresses. In these conditions, the tensile strength of the rocks may be a suitable strength parameter in RMR system to assess mechanical behavior of the rock mass in site a geotechnical work. One of the weaknesses of RMR is that it does not take into account the tensile strength of intact rock. In this paper, a new rock classification is introduced based on Brazilian tensile strength (BTS) as an alternative for point load index (PLI) in RMR. To achieve this purpose, BTS and UCS values for diverse rock types including igneous, sedimentary, and metamorphic were collected through a comprehensive review of existing literature. For each rock type, the correlation equations between BTS and UCS were developed using simple regression analysis. Using data analyses, the intact rock was categorized into seven BTS classes. The BTS classification suggested in the present study can be used as a novel approach in RMR for a rock mass outcropped at the site of a geotechnical project. This can lead to a more comprehensive assessment of the mechanical behavior of the rock mass, and therefore, a more accurate design of a geotechnical project.

Keywords

Main Subjects

Article Title [Persian]

_

Author [Persian]

  • امین جمشیدی 1
1
2
3
Geopersia

Articles in Press, Accepted Manuscript
Available Online from 05 January 2026

Files

History

  • Receive Date: 04 August 2025
  • Revise Date: 08 November 2025
  • Accept Date: 05 January 2026

Share

How to cite

Statistics