## 4 Conclusions  
This study employed the discrete element method to analyse arrester bed aggregates within typical truck escape ramps, aiming to identify key factors that influence their load-bearing capacity. By gathering detailed morphological characteristics of pebbles, this research introduced a novel method for generating random shapes that more accurately reflect their natural appearance. Additionally, leveraging the physical properties of the aggregates, this study developed an accurate discrete element model for the particles. This model effectively simulated the dynamic interactions between particles and investigated both macroscopic and microscopic elements that affect the aggregate's load-bearing capacity. Consequently, it revealed the dynamics of mechanical distribution among particles under external loads. These findings illuminate the factors impacting arrester bed performance and offer crucial insights into the design and utilization of pebble clusters, thereby facilitating the optimization of critical parameters for arrester beds. Within the limitations, the following conclusions can be drawn from this study:  
1. A novel approach for constructing DEM models of irregularly shaped particles is introduced, leveraging three-view outline curves to create three-dimensional DEM particle shapes via an overlapping element construction method. Comparison with actual particles reveals that this method effectively replicates the formation of pebbles, particularly those with smooth boundaries and flattened shapes. Furthermore, the method substantially decreases the quantity of basic units required to form the particles, maintaining shape fidelity while significantly reducing computational demands. The employment of open-top box compression tests to calibrate the microscopic parameters of the model indicates a consistent trend between experimental outcomes and simulation predictions, showcasing distinct variances under varied parametersand confirming the method's viability. Moreover, the precision of the developed pebble particle DEM models is rigorously confirmed through extensive simulation and experimental verification. 2. Leveraging the inherent material properties of these aggregates, this study provides a detailed analysis of the mechanical behavior of aggregate particles. At the macroscopic level, it conducts an analytical exploration of the stress-strain relationship curve, which is divided into two distinct phases: the'smooth phase' and the'stress phase.' The smooth phase signifies a relatively moderate growth rate, whereas in the stress phase, the contact force sharply increases, marked by several fluctuations throughout. On the microscopic scale, this study outlines the transmission pathways of external loads and the mechanical interactions between individual particle units, highlighting the particle as the primary unit of analysis. It shows that external pressures mainly affect surface-level particles initially. As the application of pressure intensifies, the distribution of force among particles becomes wider, causing a synchronous downward movement of particles under direct pressure, while adjacent ones undergo accelerated displacement. Centrally located particles experience lateral compression, leading to more subtle positional changes. 3. Integrating macroscopic and microscopic contact characteristics, this analysis delineates the process into three phases. Initially, there's a marked increase in contact forces, boosting the average force while maintaining stability. Notably, the XOY plane shows less variability than the XOZ plane, with YOZ and XOZ distributions essentially consistent, which is attributed to the particles' initial Z-axis orientation via the rainfall method. Subsequently, the rate of change in contact force decelerates due to the dispersed stress distribution, ensuring consistent average force. This uniformity stems from the pressing plate's even pressure, aligning YOZ with XOZ distributions.