## 1 Introduction  
Cement-stabilized macadam (CSM) remains the primary material used for asphalt pavement subgrade in China due to its early strength, stability, and high integrity; it is widely used in the construction of high-grade highways in China. Extensive attention has been paid to CSM's performance regarding its compressive strength [1; 2], flexural tensile strength [3; 4], resilient modulus [5; 6], durability, and shrinkage behavior [7; 8], which are closely related to the structural design and performance evaluation of semi-rigid base asphalt pavements. As a particle-based composite material, CSM's performance is directly influenced by composition structure and dense homogeneity [9]. Therefore, CSM's molding method is highly significant with regard to improving CSM's service performance. The structure and properties of cement-stabilized macadam are closely related to its molding method [10]. Current research regarding CSM forming methods remains based on comparative analysis of moisture content and compactness data from indoor tests. The results show that the physical and structural properties of CSM mixes formed using vibration are significantly better than those of mixes formed using the static pressure method [11; 12; 13; 14; 15]. Studies regarding the effect of CSM forming based on discrete element theory primarily focus on vibration molding [16]; less research has been conducted on compaction molding and comparison between the two. [PERSON] et al. used the discrete element method to simulate the vibration molding process of two-layer compacted concrete specimens, and established the discrete element model, contact model, and mesoscopic parameters of compacted concrete using the particle flow code. The embedding and movement of inter-layer aggregates under different compaction forces were analysed in the discrete element model of two-layer specimens [17]. [PERSON] et al. established a rotary compaction model of asphalt mixture by obtaining the displacement and rotation angles of coarse aggregates of different shapes in asphalt mixtures using discrete elements to analyze and simulate the movement characteristics of the aggregates [18]. [PERSON] investigated the mechanical properties of CSM based on the quasi-static compaction method (QSCM) and vertical vibratory compaction method (VVCM), and obtained quantitative indices of the mechanical properties of VVCM-formed and QSCM-formed materials [19]. [PERSON] studied the change characteristics of mesostructure in the compaction process of asphalt mixture by tracking the porosity and distribution of aggregate and asphalt mortar [20]. [PERSON] et al. summarized three main issues in the discrete element method (DEM) simulation of concrete materials: materials (mortar and coarse aggregate), contact models, and fine-view structural parameters [21]. [PERSON] et al. used the DEM to simulate the Marshall impact compaction (MIC) process and proposed a new index of the contact imbalance force of coarse aggregate particles. [PERSON] built a three-dimensional discrete element model for surface compaction experiments on soil and stone mixes, explored the effects of experimental conditions and particle fine-scale parameters on compaction effects, and proposed porosity as a quantitative index to evaluate compaction effects in simulated tests [22]. At present, CSM is usually formed using the compaction molding (quasi-static compaction) or the vibration molding method, and it is generally believed that the vibration molding method is closer to the actual construction-measured CSM compactness [23]. Current research studies the molding effect from a meso perspective; however, the mesoscopic research and analysis of the interior composition structure's characteristics and trends after molding are not sufficiently intuitive.