Speaker
Description
Significant increased of temperatures affect large crustal volumes of carbonatic rocks often related to high temperature settings (e.g volcanoes sedimentary basements, geothermal areas within thick carbonatic sequences or thick sedimentary sequences in contact with large scale plutons). Forecasting carbonatic rocks physical evolution under temperature gradients is of the utmost importance for many rock-mechanics fields, such as rock-engineering applications (deep drilling, geothermal energy and oil exploitation, nuclear waste disposal, CO2 storage) but also preservation and restoration of cultural heritages damaged by fire as well as for weakening of volcano basements and decarbonation processes during earthquake ruptures.
This study has two main objectives: the first one is the quantitative estimation of the influence of high temperatures on physical properties of texturally different carbonatic rocks and the second one to provide an unified and more comprehensive relationship between physical features and temperature.
For these purposes, carbonatic rock specimens, coming GEMEX sites and some italian analogue, were tested before and after thermal treatment, with cycles from 105°C up to 600°C, measuring porosity, ultrasonic pulse velocity (UPV) and electrical resistivity (ER).
The thermal treatment induced an increase of porosity due to generation of new cracks or re-opening of existing ones. At first sight, limestones (RLM samples) showed a marked increment in porosity compared to other samples for temperatures higher than 400°C. A plausible explanation of this behaviour is due to the fact that limestones undergo deeper textural changes, as being not exposed to heating in their formation history differently to marbles, decalcination and decarbonation processes are more pervasive and diffused between grains increasing the cracks damage.
The increase in porosity is mirrored by decrease of P- and S-wave velocity and apparent resistivity in saturated conditions.
The general degradation of physical parameters also influenced the dynamic mechanical characteristics of rock samples.
