Loading rate effect on pore space structure in rocks

Abstract

The search for the methods and modes of destruction of mineral aggregates at the minimized energy consumption is the main task of rock disintegration. According to modern ideas about the mechanism of disintegration, destruction of rocks is a process that evolves over time. From the moment of load application, the elastic and plastic deformations develop in rocks, and the elastic/plastic strain ratios depend both on the textural and structural features of rocks, and on the loading parameters. The effects of the loading rate on the pore space structure of rocks were studied. Samples of granite and gabbro-diabase were investigated. This samples had different texture, structure and porosity. The studies were performed using X-ray computer microtomography (X-ray micro-CT). This method allows obtaining quantitative values of the porosity structure – size, quantity, concentration, specific surface area of pores. The loading rate range was 0.5–5.0 mPa/s. The value of the loading force was ≈50% of the ultimate compressive strength. The load type was uniaxial compression. It is found that the porosity, as well as the number and concentration of pores under the action of axial load are reduced, the samples are compacted, small pores are closed and large non-spherical pores appear. The decrease in the total porosity and pore concentration in the samples grows with increasing loading rate. The degree of porosity reduction also depends on the structure and strength of the rocks. In granites (weaker rocks), the indicators vary greatly. In gabbro-diabase (more durable low-porous rock), the porosity parameters change less significantly.The study was supported by the Russian Science Foundation, Project No. 17-79-30056.