## 5 Numerical Simulation of Pressure Loads on Assembled Road Surfaces Underground
### Numerical Simulation  
This study utilizes ANSYS 2020 R2 numerical simulation software to construct a three-dimensional finite element model of a pavement structure composed of coal gangue concrete precast blocks and analyzes the corresponding displacement and stress distributions. Based on domestic and international research, hexagonal slabs exhibit three distinct advantages over square and rectangular slabs of equivalent area and thickness: (1) more  
Figure 11: Schematic diagram of underground road surface structure. \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & **Number** & **Diameter** & **Height** & **Poisson’s** & **Elastic Modulus** & **Strength** & **Mean** \\  & & **(mm)** & **(mm)** & **Ratio** & **(GPa)** & **(MPa)** & **(MPa)** & \\ \hline compressive & A1 & 49.90 & 99.36 & 0.282 & 23 & 43.8 & \\ strength & A2 & 48.02 & 100.16 & 0.212 & 28 & 47.4 & 43.8 \\  & A3 & 47.21 & 100.08 & 0.205 & 8 & 40.2 & \\ shear & B1 & 49.44 & 50.21 & 0.210 & n.a. & 3.9 & \\ strength & B2 & 48.90 & 50.24 & 0.195 & n.a. & 5.9 & 4.6 \\  & B3 & 50.13 & 49.36 & 0.165 & n.a. & 4.1 & \\ tensile & C1 & 49.68 & 24.22 & 0.210 & n.a. & 3.4 & \\ strength & C2 & 49.22 & 25.30 & 0.203 & n.a. & 1.8 & 2.2 \\  & C3 & 49.26 & 25.11 & 0.196 & n.a. & 1.4 & \\ \hline \end{tabular} Note: n.a.: not available.  
\end{table} 
Table 21: Mechanical parameters of the floor of the mining road. uniform internal force distribution, which enhances load-bearing performance; (2) shorter perimeter, which reduces joint defects and improves both waterproofing and freeze-thaw resistance; and (3) a greater number of edges allows for tighter joints, thereby enhancing adaptability to subgrade deformation. Given its comprehensive performance advantages and engineering feasibility, hexagonal concrete slabs were selected as the simulation subject in this study. To ensure that at least three panels are engaged under a 20 cm load radius--thereby enhancing block interaction and ensuring structural stability--the side length of each regular hexagonal slab is set to 20 cm. Given that the return airway of the 431,304 working face at Liangshuijing coal mine is 5.7 m wide, the model's planar dimensions are defined as 5.7 m \(\times\) 6.0 m. The first layer consists of regular hexagonal slabs with a side length of 20 cm and thicknesses of 12 cm, 16 cm, and 24 cm. The elastic modulus of coal gangue concrete is set to 3.5 GPa, with a Poisson's ratio of 0.23. Joints are modeled with a shear modulus of 20 MPa and anisotropic shear stiffness, incorporating vertical shear moduli Gxy and Gyz, while neglecting joint thickness and width. The sand cushion layer is 4 cm thick, with an elastic modulus of 150 MPa and a Poisson's ratio of 0.25, modeled as an anisotropic material. The elastic modulus of subgrade siltone is 26 GPa and Poisson's ratio is 0.24. The parameters used in the numerical simulation are selected from the Section 4.1. The measured results of the coal gangue fly ash block and the boundary conditions refer to the measured data of the surrounding rock constraints of the roadway. The layered distribution model of model is shown in Figure 12, the numerical analysis model is shown in Figure 13, and the material parameters of each layer are shown in Table 22.  
When conducting pavement structural mechanics analysis, this study is based on the following simplifying assumptions:  
1. Each structural layer is homogeneous, continuous, and isotropic elastic material;
2. There is complete contact between layers, with no separation or gaps;
3. The base bottom has no displacement in any direction, and the sides are fixed horizontally; concrete pavement slabs can deform freely in all directions to more realistically simulate vehicle load response;
4. The effect of the self-weight of each structural layer on the calculation results is ignored. During loading, the location at the bottom of the cement concrete slab where maximum tensile stress occurs is typically considered the critical load-bearing zone, representing a high-risk area for structural failure.