# Experimental Study on the Shear Strength of Silt Treated by Xanthan Gum during the Wetting Process
## 4 Conclusions  
A series of microscopic tests, water retention tests, and shear tests were carried out to explore the effect and mechanism of the strength characteristics of silt treated with xanthan gum. The main conclusions are as follows. The drying and wetting curves of the specimens all shifted to higher water retention capacity with increasing xanthan gum content, and the hysteretic circle area between the drying and wetting curves also gradually increased. Microscopic analysis showed that the pores of the specimens gradually filled with increasing xanthan gum content, and xanthan gum itself has strong water-retaining properties. The water retention capacity of the treated silt therefore increased. The peak strength and residual strength of the specimens gradually increase with increasing vertical stress. The shear strength, cohesion, and internal friction angle of the pure and treated silt specimens significantly increased with decreasing water content. During the wetting process, the strength of the pure and treated silt specimens all significantly weakened with increasing water content, but the strength of the treated silt was notably higher than that without treatment. The microscopic analysis showed that xanthan gum fills the uneven pores in silt during the wetting process, which makes the pore distribution more uniform and the pore structure more stable. Xanthan gum forms hydrogel bonded with the silt particles, and the cementation between the soil particles was notable, thus significantly increasing the strength of the silt treated by xanthan gum. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \multirow{2}{*}{\(\mathbf{w}\) (\%)} & \multirow{2}{*}{\(\mathbf{\sigma_{\text{v}}}\) (kPa)} & \multicolumn{3}{c}{\(m_{\text{bp}}/m_{\text{s}}\) = 0\%} & \multicolumn{3}{c}{\(m_{\text{bp}}/m_{\text{s}}\) = 2\%} & \multirow{2}{*}{**Increment of \(\mathbf{c}\)**} & \multirow{2}{*}{**Increment of \(\mathbf{\phi}\)**} \\ \cline{3-3} \cline{5-10}  & & \(\mathbf{\tau_{\text{f}}}\) (kPa) & & \(c\) (kPa) & & \(\mathbf{\phi}\) (\({}^{\circ}\)) & \(\mathbf{\tau_{\text{f}}}\) (kPa) & \(c\) (kPa) & \(\mathbf{\phi}\) (\({}^{\circ}\)) & \\ \hline \multirow{4}{*}{2} & 50 & 434.4 & \multirow{4}{*}{378.15} & \multirow{4}{*}{46.55} & 1033 & & & & \\ \cline{2-10}  & 100 & 478.5 & & & 1141 & & & & & \\ \cline{2-10}  & 200 & 591 & & & 1450 & & & & & \\ \hline \multirow{4}{*}{4} & 50 & 349 & \multirow{4}{*}{325.45} & \multirow{4}{*}{43.57} & 870.7 & \multirow{4}{*}{67.82} & \multirow{4}{*}{2.36} & \multirow{4}{*}{1.557} \\ \cline{2-10}  & 100 & 456.6 & & & & & & & \\ \cline{2-10}  & 200 & 503.7 & & & 1248 & & & & \\ \hline \multirow{4}{*}{8} & 50 & 155.2 & \multirow{4}{*}{147.3} & \multirow{4}{*}{31.05} & 155.2 & \multirow{4}{*}{165.20} & \multirow{4}{*}{31.65} & \multirow{4}{*}{1.22} & \multirow{4}{*}{1.019} \\ \cline{2-10}  & 100 & 240.8 & & & 256.9 & & & & \\ \cline{2-10}  & 200 & 256.6 & & & 278.5 & & & & \\ \hline \multirow{4}{*}{16} & 50 & 62.11 & \multirow{4}{*}{48.09} & \multirow{4}{*}{21.91} & 100.5 & \multirow{4}{*}{68.15} & \multirow{4}{*}{30.71} & \multirow{4}{*}{1.42} & \multirow{4}{*}{1.402} \\ \cline{2-10}  & 100 & 97.45 & & & & & & & \\ \cline{2-10}  & 200 & 125.5 & & & 188.3 & & & & \\ \hline \multirow{4}{*}{22} & 50 & 45.03 & \multirow{4}{*}{38.58} & \multirow{4}{*}{9.19} & 59.03 & \multirow{4}{*}{69.63} & \multirow{4}{*}{17.61} & \multirow{4}{*}{1.81} & \multirow{4}{*}{1.916} \\ \cline{2-10}  & 100 & 57.2 & & & 70.94 & & & & \\ \cline{2-10}  & 200 & 70.1 & & & 93.42 & & & & \\ \hline \end{tabular}
\end{table} 
Table 3: Strength properties of the XG- silt specimens under different conditions (\(m_{\text{bp}}/m_{\text{s}}\)). As an eco-friendly and efficient material, xanthan gum can improve the strength and stability of silt after rainfall infiltration. Therefore, xanthan gum can be used to improve the engineering properties of soil during many projects, such as deep foundation treatment, slope treatment, highway subgrade treatment, etc.