# Shear Strength Analysis and Slope Stability Study of Straight Root Herbaceous Root Soil Composite
## 3 Results
### Significance and Correlation Analysis of Shear Resistance Indicators and Influencing Factors
#### 3.3.2 Correlation Analysis between Shear Resistance Indicators and Influencing Factors  
Figure 7 presents the correlation analysis results between the shear indicators and influencing factors. The moisture content exhibits a strong positive correlation with the root burial depth (\(p=0\)), and the moisture content and root burial depth show a strong negative correlation with the internal friction angle (\(p=0\)). A weak negative correlation (\(p>0.1\)) is observed between the moisture content and root burial depth, and a significant negative correlation (\(p<0.001\)) is determined for moisture content and root burial depth with root content. The root content exhibits a strong positive correlation with the cohesion  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Undisturbed Soil**} & \multirow{2}{*}{**Moisture**} & \multirow{2}{*}{**Root**} & \multirow{2}{*}{**Internal**} & \multirow{2}{*}{**Friction**} & \multirow{2}{*}{**Cohesion/kPa**} & \multirow{2}{*}{**Cohesion/kPa**} & \multirow{2}{*}{**Failure Deviation Stress/kPa**} \\
**Sample Depth/cm** & & & & & & & & \\
**Content/\%** & & & & & & & \\  
and internal friction angle (\(p\leq 0.00001\)), while the cohesion is weakly positively correlated with the internal friction angle (\(0.01<p<0.05\)).  
The three key parameters affecting the shear strength of USRS are root content, moisture content, and root burial depth. A high moisture content promotes a deeper root system, and the root content decreases with an increase in soil depth. The reinforcement performance of the soil is reduced as the depth increases. Moreover, the rate of decrease in the internal friction angle is enhanced with a declining cohesion. A positive correlation is  
Figure 6: Summary of the cohesive force and internal friction angle data of undisturbed soil for different moisture and root contents: (**a**) cohesive force of undisturbed soil for different root contents (0%, 0.12%, 0.20%, and 0.31%) at condition I; (**b**) cohesive force of undisturbed soil for different root contents (0%, 0.11%, 0.15%, and 0.18%) at condition II; (**c**) cohesive force of undisturbed soil for different root contents (0%, 0.06%, 0.07%, and 0.09%) at condition III; (**d**) internal friction angle of undisturbed soil for different root contents (0%, 0.12%, 0.20%, and 0.31%) at condition I; (**e**) internal friction angle of undisturbed soil for different root contents (0%, 0.11%, 0.15%, and 0.18%) at condition II; (**f**) internal friction angle of undisturbed soil for different root contents (0%, 0.06%, 0.07%, and 0.09%) at condition III. Note: condition I refers to a depth of 0-20 cm; condition II refers to a depth of 20–40 cm; and condition III refers to a depth of 40–60 cm. * represents statistical significance at \(p<0.05\); ** represents statistical significance at \(p<0.001\), *** represents statistical significance at \(p<0.001\), *** represents statistical significance at \(p<0.0001\), ns represents no significant difference.  
observed between the root content and the shear strength indicators for shallow soil with a high root content. This type of soil has high slope stability. Due to the strong positive correlation between the moisture content and the root burial depth, as well as the same correlation trend with other influencing factors, we selected one of the parameters for the subsequent analysis.