Abstract
In this paper, scanning electron microscope (SEM) tests and 3D scanning technologies were adopted to investigate the creep failure mechanism of sandy mudstone from a micromesoscopic view. The SEM test results showed that the fracture surface micromorphology of the specimens that suffered creep loading was more fractured and rougher. It was also found by the fractal analysis of the SEM microscopic images that the fractal dimensions of the creep failure specimens were larger than those of the uniaxial compression failure, indicating that the creep damage increased the irregularity and a larger degree of roughness fluctuation. The 3D scanning technologies combining with the 3D reconstruction methods proved that the crack expansion path of crept specimens was more complicated, showing a more prominent asperity height and slope angle. Finally, a mesostrain dilating microelement model of the sandy mudstone specimen’s fracture surface was proposed to prove that the dilatancy effect would be more pronounced in the creep process.
Highlights
The long-term response and safety of deep engineering projects, such as nuclear waste disposal, crude oil storage facilities, and deep underground space, have attracted wide attention [1,2,3]
The mesoroughness and mesolocal inclination angle of the sandy mudstone specimens after creep failure were larger than those of the uniaxial compression failure, indicating that the dilatancy effect will be more pronounced in the creep process
This study investigated the microstructure of the fracture surface of sandy mudstone specimens under uniaxial creep conditions compared with uniaxial compression tests and showed the micromesoscopic shear dilation mechanism based on asperity and fractal theory
Summary
The long-term response and safety of deep engineering projects, such as nuclear waste disposal, crude oil storage facilities, and deep underground space, have attracted wide attention [1,2,3]. Keneti and Sainsbury [17] thought that the microstructural features, including the microcracks, veins, and healed joints, influenced the strength and failure patterns of a rock block They adopted the SEM images to characterized microscale features of the rock fragments to reveal the strain-burst mechanism. Kou et al [19] reconstructed the internal failure characteristics of the failed rock-like materials under the action of both mechanical loads and internal hydraulic pressures by using the 3D X-ray computed tomography. They adopted the fractal dimensional analysis of the 3D fragments to reveal the coupled hydromechanical fracturing mechanism. Considering the influence mechanism of the mesoroughness on the mesoshearing effect, a mesostrain-dilating microelement model of the fracture surface of a sandy mudstone specimen was constructed and the calculated mesoroughness parameters, such as the microscopic dilatancy angle and normal dilatancy deformation under uniaxial compression and uniaxial compression multistage creep conditions, were used to characterize the specimen’s fracture surface topography
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