# Numerical Analysis for Shear Behavior of Binary Interfaces under Different Bonded Conditions
## 5 Conclusions  
Due to the wide usage of concrete in rock-based engineering, rock-mortar binary interfaces under different bonded conditions have become a common occurrence, which greatly affects the stability of engineering structures. In this case, the shear performances of rock-mortar binary interfaces under different bonded conditions are investigated by PFC in this study, and the main conclusions are as follows.  
(1) Before the peak, the shear stress-shear displacement shows an obvious plastic phase for a 25% bonded interface. With the increased bonded degree of the binary interface, the plastic phase gradually disappears, and the peak displacement is also decreasing. After the peak, the greater the bonded degree of the interface, the rougher the curve in the residual stage.  
(2) Under different normal stresses, the shear strength of the binary interface increases with the increased bonded degree, which was quantitatively characterized and intuitively compared by introducing the strength factor. Additionally, the bonded condition has little influence on the friction coefficient and shows a clear positive correlation with cohesion.  
(3) Unbonded binary interfaces produce fewer cracks during shear. The cracking process at a bonded binary interface can be divided into three stages: the stress rise stage produces almost no cracks, the stress drop stage produces cracks faster and the residual stage produces cracks slowly. Bonded conditions have an effect on the crack distribution at the interface. The higher the bonded degree, the more uniform the distribution and the greater the crack number.  
(4) In the unbonded state, the stress distribution at the interface is relatively uniform. In the 50% bonded state, the stress concentration occurs at the midpoint of the interface, which may be caused by the uncoordinated deformation. In the fully bonded condition, the stress concentration region is mainly located on the left, as it is subjected to both the wall pressure and the lower block resistance. More stress concentrations may also occur elsewhere on the interface under higher normal stresses.  
Methodology, X.Z. and H.L. ([PERSON]); Software, H.L. ([PERSON]); Validation, H.L. ([PERSON]), L.H., X.Z. and H.L. ([PERSON]); Investigation, L.H. and X.Z.; Data curation, L.H.; Writing--original draft, H.L. ([PERSON]), X.Z. and H.L. ([PERSON]); Writing--review & editing, H.L. ([PERSON]), X.Z. and H.L. ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
This paper gets its funding from Project (2023)JJ30657), supported by the Hunan Provincial Natural Science Foundation of China.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
**Acknowledgments:** [PERSON], [PERSON] and [PERSON] have given many good suggestions for this paper; the authors wish to acknowledge their support.  
**Conflicts of Interest:** Author [PERSON] was employed by the company CCCC First Harbor Engineering Company Ltd. The remaining authors declare that the re-search was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.