## 2 Physical Model Experiments
### Experimental Materials and Plans
\begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{\begin{tabular}{c} **Condition** \\ **Name** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Initial Ice** \\ **Accumulation** \\ **Form** \\ \end{tabular} } & \multirow{2}{*}{**Ice Content/(\%)**} & \multirow{2}{*}{\begin{tabular}{c} **Particle-to-Chute** \\ **Bed Friction** \\ **Angle/(\({}^{\circ}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Particle-to-Chute** \\ **Sidewall Friction** \\ **Angle/(\({}^{\circ}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Angle of** \\ **Repose/(\({}^{\circ}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Flow Depth** \\ **/(m)** \\ \end{tabular} } \\ \hline M-0 & \begin{tabular}{c} Uniform \\ Accumulation \\ \end{tabular} & 0 & 23.5 & 24.4 & 33.2 & 0.037 \\ M-1 & \begin{tabular}{c} Uniform \\ Accumulation \\ \end{tabular} & 10 & 22 & 24.1 & 33 & 0.042 \\ M-2 & \begin{tabular}{c} Uniform \\ Accumulation \\ \end{tabular} & 20 & 22.5 & 25.8 & 32.2 & 0.042 \\ M-3 & \begin{tabular}{c} Uniform \\ Accumulation \\ \end{tabular} & 30 & 21.5 & 22.4 & 34.4 & 0.053 \\ M-4 & \begin{tabular}{c} Uniform \\ Accumulation \\ \end{tabular} & 40 & 20.5 & 21.6 & 26.9 & 0.058 \\ M-5 & \begin{tabular}{c} Uniform \\ Accumulation \\ \end{tabular} & 50 & 20 & 25.7 & 29.5 & 0.059 \\ M-6 & \
\begin{tabular}{c} Uniform \\ Accumulation \\ \end{tabular} & 60 & 19.5 & 24.6 & 31.2 & 0.075 \\ M-7 &
\begin{tabular}{c} Uniform \\ Accumulation \\ \end{tabular} & 70 & 18.5 & 20.8 & 28.7 & 0.075 \\ \hline \end{tabular}
\end{table} 
Table 2: Conditions of chute experiment. Figure 3: Schematic diagram of the rock-ice avalanche initiation: (**a**) Initial accumulation form: uniform mixing; (**b**) Initial accumulation form: ice on top of stones; (**c**) Initial accumulation form: stones on top of ice. The equivalent friction angles and repose angles between the particles and the base, as well as between the particles and the side walls of the flume, were determined under various experimental conditions using the methods of friction angle measurement [31] and repose angle measurement [32]. In the experimental setup, high-speed camera 2 was configured with a sampling rate of 1000 fps and a data acquisition frequency of 500 Hz, while camera 1 was set to a frame rate of 60 fps and a resolution of 4K. To ensure the accuracy of the results, several preparatory steps were taken before each trial: First, the flume slope was carefully checked to ensure it met the experimental requirements. Next, both the flume and accumulation plate were cleaned using ice-cold water at 0 \({}^{\circ}\)C and thoroughly cooled. Afterward, any residual moisture was removed with paper towels, ensuring clean and dry surfaces. Additionally, the cameras were repositioned and tested to confirm they could clearly capture the entire experimental process. The experiments were conducted indoors, with test conditions maintained between \(-3\,^{\circ}\)C and \(-1\,^{\circ}\)C. The laboratory environment, which was spacious and well-ventilated, had a temperature similar to that of the outdoors. Given that each experimental run was relatively brief, any potential effects from ice melting into liquid water were deemed negligible.