# Shearing Characteristics of Mortar-Rock Binary Medium Interfaces with Different Roughness
###### Abstract  
This study focuses on the crucial role of the shear characteristics of the mortar-rock interface (MRI) in geotechnical engineering. These properties largely determine the effectiveness of engineering reinforcement measures such as anchoring and grounding. The mechanical and deformation properties of the MRI with different roughness characteristics will be investigated. To achieve this, an indoor direct shear test was conducted on the mortar-rock binary medium (MRBM). The interface was numerically modeled from the test data using finite difference fractional value software. Direct shear simulation of the MRI by changing the normal stress (\(\sigma_{n}\)) and the sawtooth angle (\(\alpha\)) was carried out. The results showed that as the normal stress and sawtooth angle increased, the shear stiffness of the MRI also increased. The shear stiffness was found to have a linear relationship with both the normal stress and the sawtooth angle. The peak shear displacement was identified as an indirect indicator of the shear failure mode of the binary medium interface (BMI). Quantitative relationships between the shear strength (\(\tau\)), cohesion (\(c\)), angle of internal friction (\(\phi\)), residual shear strength (\(\tau_{r}\)), residual angle of internal friction (\(\phi_{r}\)), and degradation rate of the shear strength of the BMI were established based on the two influencing factors. Additionally, the study investigates how the sawtooth angle and the normal stress affect the variation in the normal displacement during direct shear testing of the MRBM. The findings revealed a correlation between the peak dilation angle of the BMI and the normal stress and sawtooth angle.  
m +
Footnote †: journal: Applied Sciences  
article  
[color=gray!20,0][  
has been investigated [34]. In terms of numerical simulation, most scholars used discrete element and finite element methods [35; 36; 37]. The particle flow method has also been used to study the \(\tau\) of specimens at the BMI under various \(\sigma_{n}\)[38]. The empirical formula for calculating the \(\tau\) of the BMI was suggested by simulating the direct shear test of the BMI with various values of the joint roughness coefficient (JRC) using the discrete element numerical simulation method [20]. In terms of theoretical research, most scholars' research directions mainly focus on the constitutive model of the binary medium interface [39; 40; 41]. The triaxial compression test was conducted on the semi-interpenetrated articulated mudstone samples, and the corresponding mechanical behavior and failure mechanism were explained. The constitutive model of the binary medium interface of the semi-interpenetrated jointed mudstone specimens has been proposed [42]. The shear stress at the BMI was found to be smaller than that at the bolt-mortar interface [43]. An energy fracture criterion is proposed for crack initiation at the MRI under consideration of viscoelastic properties [44].  
The inner pores and chemical composition of mortar and rock are uncertain, and the human factors when pouring and curing the mortar-rock binary medium specimens are also uncertain. It is also difficult to carry out repeat tests due to the influence of the test apparatus, test environment, and other factors. Therefore, experimental studies on the binary medium are greatly limited. By means of the numerical simulation software FLAC3D 3.0 for geotechnical engineering, the numerical simulation of the shear test of the BMI with more various sawtooth angles and the corresponding force of the method is carried out to extend the experimental study of the MRI.