Pore Structure Deterioration in Oil Sludge-Modified Raw Soil: A CT-Based Investigation

In order to study the mesoscale pore structure and damage evolution of modified raw soil materials incorporating cement and oil sludge, CT scanning tests are conducted on cube specimens under axial pressure. Cross-sectional CT images of the specimens at different stress stages under dynamic load are obtained, and the variation law of internal porosity of materials with different ratios is quantitatively characterized by gray scale analysis and threshold processing methods. The intrinsic relationship between porosity and material damage is established, which reveals the evolution law of damage in modified raw soil materials with stress and the corresponding failure mechanisms. The results show that: under different stress conditions, the cracks of YS1 specimens extend from the core compression zone to the edge, and YS2 specimens exhibit a “figure-eight” failure mode. The addition of oil sludge promotes the formation of a gel with strong binding capacity and plasticity, which enhances the deformability of YS2 specimens. Increasing the cement content leads to the generation of dense crystalline polymers, which results in superior mechanical performance of YS1 specimens. In the XY and YZ scanning sections, porosity variations differ significantly among specimens under different stress conditions. The damage degree of YS1 specimens increases continuously, whereas that of YS2 specimens rises initially and then declines. Although YS2 specimens exhibit lower overall damage levels, their mechanical performance remains inferior to that of YS1 specimens. Excessive oil sludge content adversely affects mechanical properties, which suggests an optimal mass ratio of oil sludge to cement of approximately 1:2.