Key Takeaways & Executive Findings
- •• A novel crack contact model incorporating linked substances is proposed, splitting crack contact into linked and unlinked portions to account for crack closure effects. • The model achieves a better compressive-to-tensile strength ratio (UCS/T) by limiting bond failure to the linked portion's contact force and moment. • Verification through contact force-displacement experiments and loading-unloading tests confirms the model's accuracy in simulating cracked rock behavior. • Simulations demonstrate the model's capability to reproduce axial and lateral strain laws and the bi-modularity of rocks, enhancing particle flow method applications.
Abstract
The models constructed by particle flow simulation method can effectively simulate the heterogeneous substance characteristics and failure behaviors of rocks. However, existing contact models overlook the rock cracks, and the various simulation methods that do consider cracks still exhibit certain limitations. In this paper, based on Flat-Joint model and Linear Parallel Bond model, a crack contact model considering linked substance in the crack is proposed by splitting the crack contact into two portions: linked portion and unlinked portion for calculation. The new contact model considers the influence of crack closure on the contact force-displacement law. And a better compressive tensile strength ratio (UCS/T) was obtained by limiting the failure of the contact bond to be solely controlled by the contact force and moment of the linked portion. Then, by employing the FISH Model tool within the Particle Flow Code, the contact model was constructed and verified through contact force–displacement experiments and loading-unloading tests with cracked model. Finally, the contact model was tested through simulations of rock mechanics experiments. The results indicate that the contact model can effectively simulate the axial and lateral strain laws of rocks simultaneously and has a relatively good reproduction of the bi-modularity of rocks.
1. Introduction
In the process of energy exploitation such as coal mining and oil exploitation, as well as in the construction of projects like tunnels and railways, rock materials are the main components and cannot be ignored. The mechanical properties of rock materials not only determine the construction schemes of the projects but also affect the safety during the construction process. However, unlike other materials, rocks typically contain a high density of micro-cracks internally, leading to complex mechanical behavior during the loading process. In engineering analysis, calculation, and simulation, understanding and accurately modeling the mechanism of crack in rocks is essential for enhancing the safety and reliability of engineering projects. Among them, the particle flow simulation method, through particle materials and contact models, is capable of simulating the heterogeneous material characteristics of rocks relatively well. This method helps researchers understand the failure mechanism of rock materials from a mesoscopic perspective, and it has been well applied in engineering simulations. However, the existing contact models lack considerations for rock cracks, which restricts their capacity to simulate the mechanisms of micro-cracks on rocks. Therefore, in order to further understand and simulate the influence of micro-cracks on the complete mechanical behavior of rocks through the particle flow simulation method, it is necessary to further combine the characteristics of micro-cracks in rocks to construct a particle contact model.
As early as in a series of papers published by Walsh [1,2], the concept regarding the effect of cracks on the mechanical properties of rocks has been essentially elaborated. When the cracks within the unit are closed under the pressure pc, the contacting crack surfaces will provide additional resistance to deformation. Therefore, the Young’s modulus of the unit will increase. For the effective modulus of the unit in the two states of single crack opening and closing, Walsh [2] performed the derivation from a three-dimensional aspect. Additionally, Bristow [3] and Jaeger et al. [4] respectively conducted studies on the effective modulus of two-dimensional units with cracks. In the above derivations, the possible slip of the crack surfaces was all taken into consideration, and it was believed that the “asymmetric” slip of the cracks during the loading process could lead to the bi-modular behavior of rocks.
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XIAO Fukun, XIE Kai, SHAN Lei, LIU Gang, LI Lianchong, FEDOTOVA Iuliia (2025). Research on rock crack contact model considering linked substances based on particle flow method. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.02.007
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Frequently Asked Questions
What is the main contribution of this paper?
The paper proposes a novel crack contact model that incorporates linked substances within cracks, splitting the contact into linked and unlinked portions to account for crack closure effects, thereby improving the simulation of rock mechanical behavior.
How does the new contact model improve upon existing models?
Existing contact models often overlook cracks or have limitations. The new model explicitly considers crack closure in the contact force-displacement law and achieves a better compressive-to-tensile strength ratio by limiting bond failure to the linked portion, leading to more accurate simulations of axial and lateral strains.
What methods were used to verify the contact model?
The model was verified through contact force-displacement experiments and loading-unloading tests with cracked models, and then tested through simulations of rock mechanics experiments.
What are the practical applications of this research?
This research enhances the particle flow simulation method for rock mechanics, which is crucial for engineering projects such as coal mining, oil exploitation, tunnel construction, and railways, improving safety and reliability.
What is the significance of the bi-modularity reproduction?
Bi-modularity refers to the different behavior of rocks under compression versus tension. The model's ability to reproduce this phenomenon is important for accurately predicting rock deformation and failure in various loading conditions.
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