## 3 Model Test Overview
### Installation of Test Devices and Measuring Points  
This experiment provides a simulation system for the vibration response of the basement structure of a heavy-haul railway tunnel. The test device is mainly composed of four parts: (1) The model box is used to simulate tunnels and surrounding rock. The length, width, and height dimensions of the box are 3.0 \(\times\) 1.5 \(\times\) 2 m. (2) Load generation devices are used to simulate the train load, which include a single-point exciter and its supporting power amplifier. (3) A data acquisition and storage system collects and stores \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type** & **Density (kg\(\cdot\)m\({}^{-3}\))** & **Elastic Modulus (MPa)** & **Poisson Ratio** \\ \hline Prototype & 2300 & 31.5 & 0.3 \\ model & 2300 & 1.58 & 0.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Physical and mechanical parameters of tunnel materials. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Density** & **Elastic Modulus** & **Poisson Ratio** & **Internal Friction Angle** & **Cohesion** \\ \cline{2-5}  & **(kN\(\cdot\)m\({}^{-3}\))** & **E (MPa)** & \(\mu\) & \(\varphi\) (\({}^{\circ}\)) & **c (kPa)** \\ \hline Prototype & & & & \\ materials & 1900 & 400 & 0.31 & 28 & 130 \\ Model & 1900 & 20 & 0.31 & 29 & 6.5 \\ materials & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Physical and mechanical parameters of surrounding rock materials. sensor information in real time. Acceleration sensors, strain gauges, soil pressure boxes, and a force sensor are used in this test. (4) For the control system, the vibration signal is managed by a computer to control the output force and frequency of the exciter. To facilitate the observation of the state of the tunnel model during the experiment, a 1.5 m \(\times\) 1.5 m plexiglass panel observation window is set on one side of the model box. The observation window has an opening according to the inner diameter of the tunnel model, and the other positions are steel plates. The pressure of the material used in the bench is greater than 0.3 MPa, and the structural deformation within this force range does not exceed 0.3 mm, which meets the required conditions for the test. The longitudinal length of the tunnel model is 1.5 m, the thickness of the overburdened soil layer is 0.5 m (corresponding to the buried depth of the prototype of 10 m), and the thickness of the lower soil is 80 cm (corresponding to the prototype thickness of 16 m). For the vibration tests, it is necessary to consider the impact of the reflection of the boundary wave of the model box on the experimental results. Duxseal is a vibration-absorbing material widely used around the world. It can absorb both shear and compression waves. The absorption effect is directly related to the thickness of the material laying. Based on the research experience of predecessors, the Duxseal material with a thickness of 3 cm is bonded to the side of the box [14; 17]. The model test bench is shown in Figure 6.  
Figure 4: Dimensions of tunnel section (m). Figure 5: The production process of the lining model: (a) positioning and assembling; (b) brushing the oil; (c) slurry stirring; (d) perfusion model. The model test uses an exciter to apply a vibration load. According to the law of driving a heavy-haul on one side, the exciter is arranged 10 cm to the left of the middle line of the tunnel model. The upper part of the exciter is fixed in place on the reaction frame. The contact between the exciter and the tunnel model can be controlled by finely adjusting the height of the anti-force frame. A force sensor is installed at the lower end of the excitation device to collect the vibration load applied by the excitation device at the bottom of the tunnel model. To obtain the dynamic response of heavy-haul railway tunnels and the surrounding soil layers with the vibration load of trains, sensors are installed in the tunnel and the surrounding soil layers.