Evolution of deformation field and energy of organic-rich oil shale under uniaxial compression

Abstract

The nonuniform distribution of organic matter in oil shale strata results in different mechanical response and failure mechanism. Uniaxial compression test, digital image correlation method and infrared thermal imaging technology were used to study the deformation field, temperature field and energy evolution characteristics of oil shale during the whole loading process under different organic matter abundances, and to reveal the influence of organic matter abundance on mechanical properties and deformation and failure mechanism of oil shale. The results show that the stress-strain characteristics of oil shale present gradual attenuation as the organic matter abundance increases, while the ductility has improved significantly. The failure mode changes from splitting tensile failure to tension-shear compound failure, which is attributed to the fact that organic matter abundance affects the control degree of bedding planes on the macroscopic crack evolution. Moreover, the deformation field and temperature field exhibit obvious localized features during loading. With the increase of organic matter abundance, the surface deformation and infrared temperature increase, and the degree of differentiation of the two fields also intensifies. In addition, organic matter abundance also affects the energy transformation and distribution of oil shale. With the increase of organic matter abundance, the energy absorption, storage and release properties weaken, while the dissipation property enhances, causing a lower overall energy state. This is the essential reason for the differences in mechanical properties and deformation and failure laws of oil shale with different organic matter abundances.

Keywords

• oil shale
• organic matter abundance
• deformation field
• temperature field
• energy characteristics