## Materials and Methods  
### Soils' Properties and Sample Preparation  
Soils for this research were collected from three test sites, i.e., Pelczynskiego, Bartycka, and Pory. Every geotechnical site name comes from the street where the construction site is located. The Pelczynskiego site is in the Bemowo district, which is located in the northeastern part of Warsaw. From this site, seven samples were collected from a depth of 2 to 7.5 m below the surface. The Pory and Bartycka sites are in the southwestern part of Warsaw, in the Mokotow district. Altogether, eight samples were collected there from a depth of 1.5 to 9.5 m below the surface. Every soil core was collected in undisturbed condition by Shelby tubes. The localization of the test sites is presented in Figure 4.  
Figure 3: Effect of plasticity index (_PI_) (%) on (**a**) damping ratio curve [16] and (**b**) threshold strains \(\gamma^{e}{}_{t}\) and \(\gamma^{e}{}_{t}\)[30]. Before performing the damping tests, the soil grain distribution and basic physical properties were examined. Based on aerometric and sieve analysis, as well as on Eurocode 7 [33; 34], every cohesive soil was recognized. Moreover, the soil parameters, moisture content according to [35], Arterberg limits according to [36], overconsolidation ratio according to [37], and initial void ratio were estimated. The soil parameters and range of mean effective stress (\(p\)) at which damping tests were conducted are presented in Table 2. In Figure 5, grain-size distribution curves for tested cohesive soils are shown. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Test Site**} & **Test** & **Depth** & **Soil Type** & **WC** & **LL (\%)** & **PL (\%)** & **PI (\%)** & \(p^{\prime}\) (**kPa)** & \(e_{0}\) (\(\star\)) & **OCR (\(\star\))** \\  & **No.** & **(m)** & **[33; 34]** & **(\%)** & **LL (\%)** & **PI (\%)** & **PI (\%)** & \(p^{\prime}\) (**kPa)** & \(e_{0}\) (\(\star\)) & **OCR (\(\star\))** \\ \hline \multirow{4}{*}{Bartycka} & _K1_ & 2.5 & saCI & 11.75 & 22.10 & 11.50 & 10.60 & 50–200 & 0.405 & 2.8–1 \\  & _K2_ & 1.5 & saCI & 18.85 & 32.75 & 15.96 & 16.80 & 30–390 & 0.562 & 1.00 \\  & _K3_ & 1.7 & clsa & 14.43 & 21.20 & 12.24 & 8.96 & 35–210 & 0.436 & 1.00 \\  & _K4_ & 6.0 & clsa & 11.06 & 17.70 & 11.10 & 6.60 & 60–240 & 0.322 & 3.33–1 \\ Pelczynskiego & _K5_ & 4.5 & saCI & 17.41 & 36.50 & 14.10 & 22.40 & 90 & 0.478 & 1.00 \\  & _K6_ & 7.5 & saCI & 10.76 & 24.50 & 12.47 & 12.03 & 75–415 & 0.304 & 2.13–1 \\  & _K7_ & 6.0 & sciCI & 17.53 & 37.25 & 17.14 & 20.10 & 120–410-120 & 0.473 & 1.3–4.42 \\  & _K8_ & 8.5 & siCI & 19.84 & 44.60 & 19.49 & 25.10 & 85–310 & 0.591 & 2–1 \\  & _K9_ & 2.2 & saCI & 12.23 & 37.00 & 11.45 & 25.60 & 45–315 & 0.365 & 1.00 \\ [PERSON] & _K10_ & 2.2 & clsa & 15.57 & 41.70 & 14.26 & 27.40 & 90–315 & 0.403 & 1.00 \\  & _K11_ & 2.2 & clsa & 10.50 & 18.20 & 9.10 & 9.10 & 45–315 & 0.429 & 1.00 \\  & _K12_ & 7.2 & siCI & 21.98 & 51.27 & 23.65 & 27.60 & 145–290 & 0.595 & 1.38–1 \\  & _K13_ & 8.0 & siCI & 22.95 & 63.50 & 26.82 & 36.70 & 160–320 & 0.634 & 1.25–1 \\  & _K14_ & 9.5 & CI & 26.04 & 70.95 & 33.11 & 37.80 & 95–285 & 0.747 & 6.32–211 \\ [PERSON] & _K15_ & 2.7 & saSICI & 12.68 & 27.10 & 12.32 & 14.80 & 55–165–55 & 0.389 & 1–3 \\ \hline \hline \end{tabular} Notes: WC—initial water content, _LL_—liquid limit, _PL_—plasticity limit, _PI_—plasticity index, \(p^{\prime}\)—mean effective stress, \(e_{0}\)—initial void ratio, and _OCR_—overconsolidation ratio.  
\end{table} 
Table 2: Basic properties and mean effective stress range for tested cohesive soils. Figure 4: The localization of geotechnical sites in Warsaw ([[https://www.google.pl/maps](https://www.google.pl/maps)]([https://www.google.pl/maps](https://www.google.pl/maps))). Figure 5: Grain-size distribution curves for tested cohesive soils. After the examination of the basic properties of the soil, the core sample was pushed out from the Shelby tube by a hydraulic press. Next, from the undisturbed core, a cylindrical specimen at 70 mm diameter and 140 mm high was cut out.