## 2 Materials and Methods  
Soils for the tests were collected from 3 test sites in Warsaw (Poland) from different depths (from 1.5 to 9.5 m). The soil cores were extracted in their undisturbed state using Shelby tubes. Before performing the damping tests in the Resonance Column, the particle size distribution of the soil and physical properties were studied. The obtained results are presented in Table 1.  
After the examination of the properties of the soil, the core sample was pushed out from the Shelby tube by a hydraulic press. Subsequently, from the undisturbed core, a cylindrical specimen at 140 mm high and 70 mm diameter was cut out. The prepared sample was placed on the resonant column pedestal. After that, the proper test was started. To prepare the specimen for testing, the resonant column chamber was closed, and the soil sample was saturated to a Skempton parameter B of at least 0.95. The consolidation process was then initiated, with dynamic tests conducted at every stage of the consolidation. First, the resonant frequency at torsional mode excitation was determined, followed by the application of a sinusoidal wave at the resonant frequency on top of the soil sample using the drive system. After seconds of excitation, the coils were switched off, and the specimen was left to vibrate freely. The damping of the soil sample movement was recorded by an accelerometer and displayed on the screen as a free vibration decay curve. The scientist then carefully selected the appropriate number of damping cycles at which specimen motions \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Test Site**} & **Test No.** & **Depth** & **soil Type** & **w\({}_{c}\)** & **LL** & **PL** & **IP** & **p\({}^{\prime}\)** & **e\({}_{o}\)** & **OCR** \\  & **No.** & **(m)** & & **(\%)** & **(\%)** & **(\%)** & **(\%)** & **(kPa)** & **(\%)** & **(\%)** \\ \hline Bartycka & S1 & 2.5 & sandy clay & 11.75 & 22.1 & 11.5 & 10.6 & 50–200 & 0.41 & 2.80–1.00 \\  & S2 & 1.5 & sandy silty clay & 18.85 & 32.8 & 16.0 & 16.8 & 30–390 & 0.56 & 1.00 \\  & S3 & 1.7 & clay sand & 14.43 & 21.2 & 12.2 & 8.9 & 35–210 & 0.44 & 1.00 \\  & S4 & 6.0 & clayy sand & 11.06 & 17.7 & 11.1 & 6.6 & 60–240 & 0.32 & 3.33–1.00 \\  & S5 & 4.5 & sandy silty clay & 17.41 & 36.5 & 14.1 & 22.4 & 90 & 0.48 & 1.00 \\  & S6 & 7.5 & sandy silty clay & 10.76 & 24.5 & 12.5 & 12.0 & 75–415 & 0.30 & 2.13–1.00 \\  & S7 & 6.0 & silty clay & 17.53 & 37.3 & 17.1 & 20.1 & 120–410-120 & 0.47 & 1.00–3.42 \\  & K8 & 8.5 & siCl & 19.84 & 44.60 & 19. & 25.11 & 85–310 & 0.5 & 2.00–1.00 \\  & S9 & 2.2 & sandy clay & 12.23 & 37.0 & 11.5 & 25.6 & 45–315 & 0.37 & 1.00 \\  & S10 & 2.2 & clay sand & 15.57 & 41.7 & 14.3 & 27.4 & 90–315 & 0.40 & 1.00 \\  & S11 & 2.2 & clay sand & 10.50 & 18.2 & 9.1 & 9.1 & 45–315 & 0.43 & 1.00 \\  & S12 & 7.2 & silty clay & 21.98 & 51.3 & 23.7 & 27.6 & 145–290 & 0.60 & 1.38–1.00 \\  & S13 & 8.0 & silty clay & 22.95 & 63.5 & 26.8 & 36.7 & 160–320 & 0.63 & 1.25–1.00 \\  & S14 & 9.5 & clay & 26.04 & 71.0 & 33.1 & 37.8 & 95–285 & 0.75 & 6.32–2.11 \\  & S15 & 2.7 & sandy silty clay & 12.68 & 27.1 & 12.3 & 14.8 & 55–165-55 & 0.39 & 1.00–3.00 \\ \hline  & & \multicolumn{3}{c}{Notes: \(w_{c}\)—initial water content, LL—liquid limit, PL—plasticity limit, IP—plasticity index, p\({}^{\prime}\)—mean effective stress, e\({}_{o}\)—initial void ratio, OCR—overconsolidation ratio.} \\ \hline  & & & & & & & & & \\ \end{tabular}
\end{table} 
Table 1: Soil characteristics and mean effective stress range for tested soils. were completely damped based on the free vibration decay curve. A detailed description of the performed research is presented in [31]. To generate a damping ratio curve, the amplitude of the applied voltage on the drive system was increased, and the same processes as described above were repeated. The damping tests were performed following the procedures outlined in [32]. Furthermore, every damping test was repeated 10 times at each shear strain.