# Instability Characteristics of and Control Techniques for Mudstone-Clay Composite Roof Roadways
## 4 Deformation and Instability Law and Prevention Technology of Double Soft Composite Roof
### Orthogonal Experimental Analysis
#### 4.1.2 Simulation Results of Roof Migration  
A numerical model was established based on the orthogonal experimental design, and FLAC3D was used for numerical simulation to determine roadway roof subsidence under different conditions. Based on the orthogonal experiment scheme in Table 4, data simulation was carried out. Figures 9-11 show displacement simulation cloud maps for various factors.  
Based on the experimental results, make a classification and comparison. In the Figures 9-11, (a), (b), and (c) represent the samples of the test piece with the same moisture content of 0%; (d), (e), and (f) represent the relative water content of 50% in both cases, while (h), (i), and (j) indicate the relative water content of 100%.  
Comparing schemes 1-3 in Figure 9, with the same layer thickness (0.4 m) and moisture content (0%), increased layer thickness leads to a larger deformation range of the roadway. Between schemes 1 and 4 (Figure 9), under the same layer thickness (0.4 m) and depth (1.5 m), roadway deformation increases with higher water content. Schemes 7-9 in Figure 9 demonstrate that roadway deformation increases with the number of layers under different layer conditions. Scheme 9 in Figure 9 shows a significant arc-shaped sinking, reaching a maximum deformation of 443.82 mm and exhibiting the largest variation range.  
\begin{table}
\begin{tabular}{c} **Moisture** \\ Cont \\ \end{tabular} & Horizon \\ \hline
18 & 0.4 m & 0\% & 1.5 m & 10\# & 0.8 m & 0\% & 1.5 m & 19\# & 1.2 m & 0\% & 3.0 m \\ \hline
28 & 0.4 m & 0\% & 3.0 m & 11\# & 0.8 m & 0\% & 4.5 m & 20\# & 1.2 m & 0\% & 3.0 + 4.5 m \\ \hline
38 & 0.4 m & 0\% & 4.5 m & 12\# & 0.8 m & 0\% & 1.5 + 3.0 m & 21\# & 1.2 m & 0\% & 1.5 + 3.0 + 4.5 m \\ \hline
48 & 0.4 m & 50\% & 1.5 m & 13\# & 0.8 m & 50\% & 3.0 m & 22\# & 1.2 m & 50\% & 1.5 m \\ \hline
56 & 0.4 m & 50\% & 4.5 m & 14\# & 0.8 m & 50\% & 3.0 + 4.5 m & 23\# & 1.2 m & 50\% & 3.0 m \\ \hline
64 & 0.4 m & 50\% & 1.5 + 3.0 m & 15\# & 0.8 m & 50\% & 1.5 + 3.0 + 4.5 m & 24\# & 1.2 m & 50\% & 1.5 + 4.5 m \\ \hline
78 & 0.4 m & 100\% & 3.0 m & 16\# & 0.8 m & 100\% & 1.5 m & 25\# & 1.2 m & 100\% & 1.5 m \\ \hline
88 & 0.4 & 100 & 3.0 + 4.5 m & 17\# & 0.8 & 100 & 3.0 m & 26\# & 1.2 m & 100\% & 4.5 m \\ \hline
99 & 0.4 & 100 & 1.5 + 3.0 + 4.5 m & 18\# & 0.8 & 100 & 1.5 + 4.5 m & 27\# & 1.2 m & 100\% & 1.5 + 3.0 m \\ \hline \hline \end{tabular}
\end{table}
Table 4: Orthogonal experimental scheme.  
Figure 9: A simulation cloud map with a layer thickness of 0.4 m.  
Figure 10 shows that with 0.8 m clay layer thickness, scheme 18 (relative moisture content of 100%, layer 1.5 + 4.5 m) displays substantial deformation with maximum roof displacement of 592.96 mm, showing the greatest variation under 0.8 m thickness. Figure 11 indicates at 1.2 m clay layer thickness, scheme 27 (relative moisture content of 100%, layer 1.5 + 3.0 m) shows the most significant deformation with symmetrical displacement characteristics reaching a maximum deformation of 1103.20 mm, the highest among all schemes. Overall, scheme 27 exhibits the most pronounced roadway deformation in the orthogonal experiment. The maximum roadway displacement variations are summarized in Table 5.  
Figure 11: A simulation cloud map with a layer thickness of 1.2 m.  
Figure 10: A simulation cloud map with a layer thickness of 0.8 m.