# Shear Strength Analysis and Slope Stability Study of Straight Root Herbaceous Root Soil Composite
## 3 Results
### Slope Stability of Plant Roots
#### 3.4.2 Results for Different Working Conditions
When the slope safety coefficient reaches the critical value of 1.0, the slope angle of the fitted curve is 0.8\({}^{\circ}\) larger for condition VIII than for condition I, indicating a 1.5% increase in the slope angle of bare soil. Figure 11: Equivalent plastic strain cloud diagram of slope instability under representative working conditions: (**a**) condition I; (**b**) condition IV; (**c**) condition VI; (**d**) condition VIII; (**e**) condition I *; (**f**) condition IV *; (**g**) condition VI *; (**h**) condition VIII *; (**i**) condition I **; (**j**) condition IV **; (**k**) condition VI **; (**l**) condition VIII **. Figure 12: Slope safety coefficients under different working conditions: (**a**) \(\beta\) = 40\({}^{\circ}\); (**b**) \(\beta\) = 45\({}^{\circ}\); (**c**) \(\beta\) = 50\({}^{\circ}\). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Conditions**} & **MEPS** & **Decreasing** & \multirow{2}{*}{**MHD/m**} & **MHD** & \multirow{2}{*}{**MVD/m**} & **MVD** \\  & **During** & **Propor-** & & & **Reduction** & **MVD/m** & **Reduction** \\  & **Instability** & **tion/\%** & & & **Ratio/\%** & & **Ratio/\%** \\ \hline I & 0.636719 & — & 0.032375 & — & 0.114286 & — \\ II & 0.635391 & 0.2 & 0.031437 & 2.9 & 0.113143 & 1.0 \\ III & 0.553426 & 13.1 & 0.030902 & 4.6 & 0.110315 & 3.5 \\ IV & 0.547221 & 14.1 & 0.030469 & 5.9 & 0.107667 & 5.8 \\ V & 0.543657 & 14.6 & 0.029738 & 8.1 & 0.105729 & 7.5 \\ VI & 0.428600 & 32.7 & 0.029411 & 9.2 & 0.102663 & 10.2 \\ VII & 0.375418 & 41.0 & 0.028764 & 11.2 & 0.101534 & 11.2 \\ VIII & 0.324946 & 49.0 & 0.028131 & 13.1 & 0.099503 & 12.9 \\ I \({}^{*}\) & 0.601005 & — & 0.023168 & — & 0.111812 & — \\ II \({}^{*}\) & 0.549951 & 8.5 & 0.022704 & 2.0 & 0.110247 & 1.4 \\ III \({}^{*}\) & 0.544128 & 9.5 & 0.022046 & 4.8 & 0.107160 & 4.2 \\ IV \({}^{*}\) & 0.510160 & 15.1 & 0.021649 & 6.6 & 0.105874 & 5.3 \\ V \({}^{*}\) & 0.491878 & 18.2 & 0.021173 & 8.6 & 0.102803 & 8.1 \\ VI \({}^{*}\) & 0.461537 & 23.2 & 0.020537 & 11.4 & 0.100131 & 10.4 \\ VII \({}^{*}\) & 0.457528 & 23.9 & 0.020188 & 12.9 & 0.097727 & 12.6 \\ VIII \({}^{*}\) & 0.323477 & 44.7 & 0.019946 & 13.9 & 0.095284 & 14.8 \\ I \({}^{**}\) & 0.781474 & — & 0.019870 & — & 0.119784 & — \\ II \({}^{**}\) & 0.662149 & 15.3 & 0.019314 & 2.8 & 0.116310 & 2.9 \\ III \({}^{**}\) & 0.651890 & 16.6 & 0.019101 & 3.9 & 0.113635 & 5.1 \\ IV \({}^{**}\) & 0.640430 & 18.0 & 0.018796 & 5.4 & 0.110681 & 7.6 \\ V \({}^{**}\) & 0.544342 & 30.3 & 0.018476 & 7.0 & 0.109020 & 9.0 \\ VI \({}^{**}\) & 0.535788 & 31.4 & 0.018033 & 9.2 & 0.105750 & 11.7 \\ VII \({}^{**}\) & 0.475997 & 39.1 & 0.017690 & 11.0 & 0.104164 & 13.0 \\ VIII \({}^{**}\) & 0.329235 & 57.9 & 0.017372 & 12.6 & 0.102601 & 14.3 \\ \hline \hline \end{tabular} Note. \({}^{*}\) slope angle of 40\({}^{\circ}\), \({}^{**}\) slope angle of 50\({}^{\circ}\); the normal slope is 45\({}^{\circ}\).  
\end{table} 
Table 8: Maximum horizontal and vertical displacements (MHD and MVD) for different working conditions and maximum equivalent plastic strain (MEPS) during instability. Figure 13: Slope safety coefficients for eight working conditions and different slope angles. Note: I-VIII represent different working conditions under a constant slope angle. The reinforcement effect by the root system results in a 3.2-11.2% increase in the safety coefficient and improved stability of slopes with an angle exceeding 1.5%. Therefore, using roots for slope reinforcement prevents the sliding surface from moving within the buried depth range of the root system and improves slope stability.