## 6 Conclusions  
This study mainly focuses on two aspects. First, to ensure the accuracy and validity of the numerical simulation, the parameters of the diorite HJC model in the Jinan area were determined. Secondly, the numerical simulation of a disc cutter with different blade widths and blade fillets was carried out using the parameters of the diorite HJC model in the Jinan area. The main conclusions of this study are enumerated below.  
(1) The basic physical and mechanical parameters, the strain rate constant, the limit surface parameters, state equation parameters and damage model constants of diorite in the Jinan region were obtained by means of a series of experiments. Compared with previous numerical simulation studies on rock-breaking using disc cutters, this study obtained simulation results closer to the actual situation by measuring the rock parameters encountered in the actual project.  
(2) The influence of the penetration degree on the contact force of the disc cutter and its range and standard deviation were investigated. With increasing penetration, the contact force of the disc cutter gradually increases, and the range of contact force fluctuates slightly and increases, but the standard deviation of the contact force remains stable.  
(3) The influence of blade fillet and blade width on the rock-breaking behaviour of the disc cutter was analysed. When the penetration was the same, the larger the blade fillet, the smaller the contact force, as well as the range and the standard deviation of contact force. The influence range of the disc cutter during rock breaking decreases with increasing blade fillet. At the same penetration depth, the wider the blade width, the greater the contact force, range of contact force and standard deviation of contact force. Moreover, the influence range of the disc cutter during rock breaking increases with increasing blade width.  
(4) The influence law of each factor described in this paper on the rock-breaking behaviour of the disc cutter provides a certain reference for the selection of disc cutters in future shield projects.  
It is hoped that the research on the influencing factors of rock-breaking by disc cutters in this paper will be able to provide a certain reference for engineering in the construction of shield tunnels. The current research is mainly limited to the rock-breaking simulation of a single disc cutter, with the simulated cutter being an 18-inch disc cutter, and the research results were not further verified by laboratory experiments. In future research, the rock-breaking behaviour of 17-20 inch disc cutters should be explored extensively and in detail, in order to provide more effective and specific guidance for practical engineering. At the same time, research on the rock-breaking behaviour of groups of disc cutters should be carried out, and the overall rock-breaking ability and rock-breaking effect of the shield should be further discussed in a more macro and specific manner.  
Methodology, Y.D.; Software, J.W.; Investigation, X.D.; Resources, B.W. and Z.S.; Funding acquisition, D.Y. All authors have read and agreed to the published version of the manuscript.  
This work was supported by Shandong Provincial Key Research and Development Program [grant numbers No. 2021 CXGC010209]; the National Natural Science Foundation of China [grant numbers No. 52278389]; and the Ministry of Housing and Urban-Rural Development [grant numbers No. 2020-K-142].  
Not applicable.  
The data presented in this study are available from the corresponding author upon request.  
The authors declare that they have no conflict of interest to report regarding the present study.