Abstract
Dilation behavior is of great importance for reasonable modeling of the stability of the host rock of the repository for high-level radioactive waste disposal. It is a suitable method for carrying out direct shear experiments to analyze the dilation behavior of rock with well understood physical meanings. Based on a series of direct shear experiments on granite samples from the Alxa candidate area under different normal stresses, the shear stress‒shear strain and shear stress‒normal strain relations have been studied in detail. Five typical stages have been divided associated with the fracturing process and deformation behaviors of the granite samples during the experimental process, and the method to determine the typical stress thresholds has been proposed. It has also been found that the increasing normal stress may reduce the maximum dilation angle, and when the normal stress is relatively lower, the negative dilation angle may occur during the post-peak stage. According to the data collected from the direct shear tests, an empirical model of the mobilized dilation angle dependent on normal stress and plastic shear strain is proposed. This mobilized dilation angle has clear physical meanings and can be used in plastic constitutive models of the host rock of the repository, and this analysis can also be put forward to other types of geomechanical problems, including the deformation behaviors related to landslide, earthquake, and so on.
Highlights
The results presented show that this range of normal stresses is suitable enough to conduct a systematic analysis of the dilation behavior of these granite samples
Based on the definition in Equation (4), a series of plastic normal strain and plastic shear strain values should be obtained in order to analyze the dilation behavior of the granite samples under the direct shear experiments
Alxa candidate candidate area in disposal, this paper supplied a systematic analysis of the shear stress–shear area in China for high-level radioactive waste (HLW) disposal, this paper supplied a systematic analysis of the shear stress–shear strain and shear stress–normal strain relations
Summary
Extensive studies on the geological disposal of high-level radioactive waste (HLW) have been carried out for several decades [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28]. Many previous researches have been carried out based on conventional tri-axial compression experiments on cylindrical rock samples. According to these experimental studies, different stages of stress-strain relations have been divided, and dilation behaviors have been studied associated with the process of crack propagation and acoustic emission events during the compression [1,35,37,38]. These studies are mainly on the phenomenological and mechanism
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