单轴压缩下富有机质油页岩变形场与能量演化特征研究

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

油页岩矿层中有机质的不均匀分布导致岩石的力学响应与破坏机制有所差异。为此,综合运用单轴压缩试验、数字图像相关方法及红外热成像技术,研究不同有机质丰度下油页岩加载全程的变形场、温度场及能量演化特征,揭示有机质丰度对油页岩力学特性与变形破坏机制的影响。研究表明:随着有机质丰度增高,油页岩的应力-应变特征总体呈现衰减趋势,延展性显著提升;破坏模式从劈裂型张拉向张拉-剪切复合型发展,这归因于有机质丰度改变了层理弱面对宏观裂纹发育的控制程度。变形场和温度场在加载作用下具有明显的局部化特征,表面变形量、红外温度均随有机质丰度增高而增大,两场分异程度也随之增强。此外,有机质丰度也影响着油页岩的能量转化及分配规律,随着有机质丰度增高,油页岩的吸能、储能及释能性质减弱,而耗能性质增强,整体能量状态降低。这是不同有机质丰度的油页岩力学特性与变形破坏规律存在差异的本质诱因。

The uneven distribution of organic matter in oil shale strata results in different mechanical response and failure mechanism.Uniaxial compression test,digital image correlation and infrared thermal imaging 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.