# A Study on the Creep Characteristics of Gassy Clay Mixed with Silt
## 4 Discussions  
This paper uses the silty clay of a borehole 8.1-29.9 m deep in a super-large diameter cross-river tunnel project as raw soil, combines the laboratory \"zeolite method\" to prepare silt-containing gassy clay, and studies the mechanical properties of gassy soil such as triaxial shear strength and long-term creep strength based on triaxial shear tests and creep tests, combined with test results, theoretical analysis, and prediction models. The main research results are as follows:  
(1) Indoor geotechnical tests were conducted on the raw soil to measure its basic physical and mechanical indicators. The process of preparing silt-containing gassy clay \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Test No.** & **Gas Content** & **Confining Pressure** & \begin{tabular}{c} **Measured Strength** \\ **in Reference** \\ \end{tabular} & \
\begin{tabular}{c} **Calculated Strength** \\ **in Reference** \\ \end{tabular} &
\begin{tabular}{c} **Relative Error** \\ **(kPa)** \\ \end{tabular} \\ \hline
21 & 25 & 200 & 75 & 67.80 & 9.59 \\
22 & 25 & 200 & 71 & 67.80 & 4.50 \\
26 & 25 & 200 & 76 & 67.80 & 10.78 \\
33 & 30 & 400 & 170.5 & 147.30 & 13.61 \\
34 & 30 & 400 & 172.5 & 147.30 & 14.61 \\
37 & 30 & 400 & 161.5 & 147.30 & 8.79 \\
38 & 30 & 400 & 169 & 147.30 & 12.84 \\
46 & 25 & 200 & 76 & 67.80 & 10.78 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Literature data verification of Equation (9) of silt-containing gassy clay. Figure 9: Error bar figure of calculated values of long-term strength of gassy clay. by the \"zeolite method\" was introduced. At the same time, the composition ratio table of each component when preparing the soil sample and the pretreatment method of the soil sample before the triaxial test were given before the test. (2) The triaxial test results show that the increase in confining pressure and the decrease in gas content both increase the yield stress value of silt-containing gassy clay, and the stress-strain curve relationship presents a typical strain hardening type, revealing the influence of gas content on the mechanical properties of silt-containing gassy clay, providing a basis for subsequent creep tests. (3) From the full-process creep curve, it can be seen that the increase in gas content and confining pressure has the opposite effect on soil deformation. When other conditions are the same, the increase in confining pressure makes the deformation of silt-containing gassy clay smaller; similarly, when other conditions are the same, the increase in gas content makes the deformation of silt gas-containing clay faster. This phenomenon is due to the fact that high confining pressure can better suppress the lateral deformation of the soil and keep the soil stable, while the presence of gas in the soil changes the relatively stable state of the soil itself. The presence of gas in the soil causes the internal structure of the soil to be destroyed, and the strength of the soil is reduced, and the degree of damage increases with the increase in gas content. (4) From the stress-strain isochronal curve, it can be seen that the increase in confining pressure has a positive effect on the structural stability of the soil, while the presence of gas weakens the structural strength of the soil itself, causing the structural attenuation of the soil under low deviatoric stress loading, which accelerates the deformation of the soil. In addition, the long-term strength is selected according to the stress-strain isochronous curve cluster method. When the gas content is constant, the long-term strength of the soil is positively correlated with the confining pressure; when the confining pressure is constant, the long-term strength of the soil is negatively correlated with the gas content. (5) By analyzing the test results, a predictive relationship between the conventional triaxial yield stress of silt clay and the gas content and confining pressure was established, and the prediction effect was verified to be good.