Influence of thermal treatment on behavior of stress‑lateral strain curve in crystalline marble rock using experimental and numerical modeling

Bijan Dehghani^*1. Lohrasb Faramarzi¹. Danial Mohammadzamani¹. Ehsan¹

¹Department of Mining Engineering, Isfahan University of Technology, Isfahan, Iran

Doi:10.1007/s12517-021-08755-z

Abstract
The structure of different rock types could be altered due to natural or man-made thermal effects. Investigating the behavior of stress–strain curve in rocks which is obtained from uniaxial compressive strength (UCS) test is, therefore, a crucial task to be applicable in geotechnical and geomechanical projects. This study deals with the impact of thermal treatment on lateral strain of crystalline marble specimen during UCS test. Firstly, samples were heated up to 160 and 500 °C and then cooled down to room temperature. Microscopic observation of samples was also provided to investigate the process which takes place in crystals during thermal treatment. The results showed that during loading, for samples which were heated up to 160 °C, a reduction in the lateral strain occurred which was up to one-third of ultimate strength (20 MPa), and after that, a gradual increase was observed in the lateral strain. In samples which were heated up to 500 °C, however, this reduction continued to one-seventh of ultimate strength (5 MPa), and subsequently, there was a dramatic growth in the lateral strain. Samples at the room temperature showed a completely different trend than thermally treated ones. Numerical modelling was also carried out in two approaches to verify the experimental results. In the first approach, the effect of thermal treatment is applied to sample by changing parameters such as shear and normal stiffness, whereas in the second method, the thermo-mechanical coupling is taken into account. The numerical results showed that the ratio of normal-to-shear stiffness has the most significant role in simulating the stress-lateral strain behavior, and modelling based on the thermo-mechanical coupling was coincided with stress-lateral strain curve behavior extracted from experimental results.

Keywords: Thermal treatment. Lateral strain. Intergranular and intragranular micro-cracks. Crystalline marble. Thermomechanical coupling