## 2 Methods and Materials
### Characteristics of the Tested Cohesive Soils
#### 2.3.3 Stegny Site  
The Stegny test site is located in the Vistula valley, on a floodplain terrace in the southern part of Warsaw. The cohesive soils tested occur in a glaciotectonically disturbed area and represent stiff Pliocene clays covered with fine and medium sands from the Wurm-Vistula Glaciation period, with a thickness of 4.0-5.0 m. Pliocene clays are classified as high plasticity clays. The groundwater table was found at the depth of 3 m. Grain size distribution of the tested soils (Figure 3) shows that according to EN ISO 14688-1 and 2 Standards [52; 53], the cohesive soils are classified as silty clays (siCl) and clays (Cl). The index properties of the tested soils for three undisturbed soil samples (No. 14-16) are shown in Table 2. The glacitectonically disturbed Pliocene clays are preconsolidated with the overconsolidation ratio, \(OCR\), increasing with depth from 5 to 8.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Soil Type** [53]} & \multirow{2}{*}{**Depth**} & \multirow{2}{*}{\(w_{\pi}\)} & \(w_{L}\) & \(w_{P}\) & \(I_{C}\) & \multicolumn{3}{c}{**Fraction [52]**} & \multicolumn{3}{c}{**Activity**} \\  & & & & (\%) & (\%) & (\%) & (\%) & (\%) & & (\%) & & **(\%)** & & **A (\(\ast\))** \\ \cline{5-12}  & & \multicolumn{3}{c}{**(m)**} & & & & & & & & & **Gr** & **Sa** & **Si** & **Cl** & \\ \hline \multicolumn{12}{c}{Urysnów site–Auditorium} \\ \cline{5-12}
1 & clsa/sasiCl & 5.0–5.3 & 10.3 & 25.2 & 12.8 & 12.4 & 1.20 & 1 & 59 & 27 & 13 & 0.95 \\
2 & clsa & 5.3–5.7 & 8.6 & 24.1 & 11.9 & 12.2 & 1.27 & 1 & 63 & 25 & 11 & 1.11 \\
3 & clsa & 7.0–7.4 & 10.4 & 24.9 & 11.9 & 13.0 & 1.11 & 0 & 61 & 28 & 11 & 1.18 \\  & & \multicolumn{3}{c}{Urysnów site–Building No. 37} & & & & & & & & & \\
4 & clsa & 6.5–6.9 & 9.0 & 25.1 & 11.7 & 13.4 & 1.20 & 1 & 68 & 20 & 11 & 1.22 \\
5 & sasiCl & 7.0–7.4 & 10.4 & 24.6 & 11.9 & 12.7 & 1.12 & 1 & 58 & 30 & 11 & 1.15 \\
6 & sasiCl & 8.5–8.9 & 9.9 & 26.5 & 12.4 & 14.1 & 1.18 & 2 & 58 & 29 & 11 & 1.28 \\  & & \multicolumn{3}{c}{Urysnów site–Building No. 34} & & & & & & & & & \\
7 & clsa & 6.5–6.9 & 10.3 & 24.9 & 12.9 & 12.0 & 1.21 & 1 & 66 & 23 & 10 & 1.20 \\
8 & clsa/sasiCl & 7.0–7.4 & 10.5 & 23.1 & 12.0 & 11.1 & 1.13 & 1 & 60 & 28 & 11 & 1.01 \\
9 & sasiCl & 8.0–8.4 & 9.4 & 26.6 & 13.1 & 13.5 & 1.27 & 1 & 59 & 28 & 12 & 1.12 \\  & & \multicolumn{3}{c}{Bielany site} & & & & & & & & & \\
10 & sasiCl & 15.0–15.4 & 10.4 & 30.9 & 13.1 & 17.8 & 1.15 & 1 & 52 & 31 & 16 & 1.11 \\
11 & siCl & 7.1–7.6 & 19.2 & 38.0 & 18.8 & 19.2 & 0.98 & 0 & 7 & 73 & 20 & 0.96 \\
12 & siCl & 8.5–8.9 & 21.1 & 34.6 & 17.5 & 17.1 & 0.79 & 0 & 7 & 73 & 20 & 0.86 \\
13 & sasiCl & 12.0–12.5 & 11.4 & 27.7 & 12.3 & 15.4 & 1.05 & 1 & 57 & 29 & 14 & 1.10 \\  & & \multicolumn{3}{c}{Stegny site} & & & & & & & & & & \\
14 & Cl & 6.0–6.4 & 26.0 & 78.4 & 25.9 & 52.5 & 1.00 & 0 & 2 & 50 & 48 & 1.09 \\
15 & Cl/siCl & 9.0–9.4 & 28.5 & 88.1 & 31.2 & 56.9 & 1.05 & 0 & 6 & 57 & 37 & 1.54 \\
16 & Cl/siCl & 12.0–12.4 & 19.8 & 67.6 & 25.5 & 42.1 & 1.13 & 0 & 3 & 59 & 38 & 1.11 \\ \hline \hline \end{tabular} Notes: \(w_{\pi}\)—water content, \(w_{\pi}\)—liquid limit, \(w_{P}\)—plastic limit, \(I_{P}=w_{L}\)–\(w_{P}\)—plasticity index, \(I_{C}=(w_{L}\)–\(w_{P})\)/\(I_{P}\)—consistency index, Gr—gravel, Sa—sand, Si–silt, Cl—clay, \(A=I_{P}\)/\(I_{C}\)—activity, \(f_{C}\)—percent of clay fraction, 1–16—number of tested cohesive soil.  
\end{table}
Table 2: Index properties of the tested cohesive soils.