Paper contribution

Pre-Peak Nonlinearity of Granodiorite in Mohr–Coulomb and Hoek–Brown Models

A. Z. Ter-Martirosyan; G. O. Anzhelo; L. YU. Ermoshina; Viacheslav Lunin

Proceedings
EUROCK 2026
Pages
681-686
Submitted
3 July 2026
Accepted
15 June 2026
Published
12 August 2026

Summary

Abstract

This paper addresses the use of laboratory-derived deformation parameters of rock specimens for selecting constitutive models in numerical stress–strain analysis. The experimental basis of the study consists of uniaxial compression tests performed on water-saturated cylindrical granodiorite specimens. The tests provided the uniaxial compressive strength, the deformation modulus along the loading branch, the elastic modulus along the unloading branch, the transverse deformation coefficient, and Poisson’s ratio. Analysis of the stress–strain curves shows that the pre-peak behaviour of granodiorite cannot be reduced to a linear elastic response governed by a single constant deformation modulus. A pronounced nonlinear segment is observed at the initial loading stage, which may be associated with the closure of microcracks, pores, and weakened contacts within the rock structure. At the same time, the deformation modulus determined within the standard stress range mainly characterizes the working part of the curve and does not represent the initial deformation stage. It is shown that the Mohr–Coulomb model and the standard Hoek–Brown model may be used for engineering assessment of limit states and for parametric analysis; however, their application is limited when the objective is to reproduce the complete pre-peak uniaxial compression curve. As a promising direction, the use of models with stiffness evolution is proposed, including modified Hoek–Brown with softening formulations supplemented by a pre-peak deformation modulus evolution law.

Contributors

Authors

  1. A. Z. Ter-Martirosyan Moscow State University of Civil Engineering, Russian Federation ORCID 0009-0006-9352-332X
  2. G. O. Anzhelo Moscow State University of Civil Engineering, Russian Federation
  3. L. YU. Ermoshina Moscow State University of Civil Engineering, Russian Federation
  4. Viacheslav Lunin Moscow State University of Civil Engineering, Russian Federation

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