## 3 Mechanical Parameters of Deep Hole Soil  
### Analysis of Soil Basic Physical and Mechanical Parameters  
Physical and mechanical tests were carried out in accordance with the Geotechnical Testing Procedures (SL237-1999). Basic physical and mechanical parameters such as the natural water content, natural density, soil grain specific gravity, liquid limit, plastic limit, plastic index and burning loss of soil were tested for each depth of soil. The liquid limit is measured according to the water content corresponding to the sinking of 10 mm by the 76 g watt conical instrument commonly used in China. The basic physical and mechanical parameters of the soil are shown in Table 2. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{\begin{tabular}{c} **Depth** \\ **(m)** \\ \end{tabular} } & \multirow{2}{*}{**Color**} & \multirow{2}{*}{\begin{tabular}{c} **Soil** \\ **Classification** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Water** \\ **Content** \\ \end{tabular} } & \multirow{2}{*}{**Density**} & \multirow{2}{*}{\begin{tabular}{c} **Specific** \\ **Gravity** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Liquid** \\ **Limit** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Plastic** \\ **Index** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Plastic** \\ **Loss** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Buming** \\ **Loss** \\ \end{tabular} } \\ \cline{5-10}  & & & & & **(\%)** & & & **(\%)** & & **(\%)** \\ \hline
1 & 0.50 & brown-yellow & silt & 11.4 & 1.74 & 2.69 & 26.5 & 20.5 & 6.0 & \\
2 & 2.60 & brown-yellow & silt & 31.8 & 1.76 & 2.70 & 39.3 & 32.2 & 7.1 & \\
3 & 19.10 & brown-yellow & clay & 31.7 & 1.90 & 2.73 & 41.0 & 23.7 & 17.3 & \\
4 & 20.80 & brown-yellow & silt & 18.3 & 1.98 & 2.69 & 22.5 & 17.0 & 5.5 & \\
5 & 44.54 & brown-yellow & silt & 16.6 & 2.10 & 2.70 & 28.2 & 19.4 & 8.8 & \\
6 & 45.46 & brown-yellow & silt & 23.2 & 1.96 & 2.70 & 30.0 & 21.1 & 8.9 & \\
7 & 46.55 & brown-yellow & silt & 23.6 & 1.92 & 2.70 & 31.2 & 22.3 & 8.9 & \\
8 & 49.73 & brown-yellow & silty clay & 21.6 & 1.96 & 2.71 & 29.5 & 16.0 & 13.5 & \\
9 & 63.19 & brown-yellow & silt & 24.0 & 1.95 & 2.70 & 30.5 & 21.7 & 8.8 & \\
10 & 65.67 & brown-yellow & silty clay & 21.8 & 2.05 & 2.72 & 35.0 & 18.7 & 16.3 & \\
11 & 67.64 & brown-yellow & clay & 23.5 & 2.00 & 2.73 & 39.4 & 22.0 & 17.4 & \\
12 & 99.20 & brown-yellow & clay & 27.1 & 1.99 & 2.74 & 47.1 & 25.9 & 21.2 & \\
13 & 100.50 & grey & clay & 25.5 & 1.95 & 2.73 & 41.1 & 23.3 & 17.8 & 4.2 \\
14 & 101.65 & brown-yellow & clay & 25.2 & 1.94 & 2.73 & 39.8 & 21.6 & 18.2 & \\
15 & 106.66 & grey-yellow & silt & 21.5 & 2.02 & 2.69 & 30.3 & 24.0 & 6.3 & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Basic physical and mechanical parameters of soil. According to the experimental results, we analyzed the variation trend of the basic physical and mechanical parameters of the soil with depth. Different types of soil have different physical and mechanical properties, so we divided soils into three categories: silt, silty clay and clay, and analyzed their laws, respectively (Figure 4). The classification standard of soil was carried out in accordance with the Code for Investigation of Geotechnical Engineering (GB 50021-2001), (2009 edition) [32]. As can be seen from Figure 4, the basic mechanical parameters of silt are relatively discrete due to its characteristics of a high silt particle content, low cohesion and easy disturbance. However, on the whole, the natural density of all kinds of soil has little change with the increase of depth. In particular, the density of clay changes little with depth, indicating that the soil is in a good consolidation state and belongs to normal consolidation or over-consolidation. At the same time, the liquid and plastic limits of clay are generally larger than those of silt and silty clay, and fluctuate with the burial depth.