## 4 Tests Results and Discussion  
In Tables 3 and 4, a summary of the \(V_{S}\) values obtained by various techniques of travel time determination is presented. The data combined in Table 3 concern the first three specimens, namely of pure RCA, while those of Table 4 relate to three mixtures of RCA with rubber chips. All the results are resumed here, regardless of whether \(L_{TT}/\lambda\) ratio is greater than 3.0 or not. The wave periods employed in the presented tests, divided into two groups: for specimens No. 1, 4, 6 and for specimens No. 2, 3, 5, arise from the authors' experience and the possibility of clear wave reading. From Tables 3 and 4, it can be noted that the \(V_{S}\) values are not uniform for different periods. Figure 7: “Unwrapped” phase in cross-spectrum method. An example of test results from pure RCA specimen No. 2, \(T=0.16\) ms, \(p^{\prime}=90\) kPa. Moreover, a comparison of the \(V_{S}\) results obtained by peak-to-peak method, but done twice, shows a big consistency of the values of shear wave velocity. The average difference between the velocities from the technique peak-to-peak\(\_1\) and peak-to-peak\(\_2\) does not exceed 0.5%, what can be also confirmed in the next presented tables. It follows that it does not matter when the analysis of the signals is performed, during or after the tests. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & & & & & & & & & & & & & & & \\ \hline \multirow{4}{*}{**Pure RCA No. 1**} & \multirow{4}{*}{\(\frac{\text{\bf{Pure RCA No. 2}}}{\text{\bf{Pure RCA No. 3}}}\)} & \multirow{4}{*}{\(\frac{\text{\bf{Pure RCA No. 3}}}{\text{\bf{Pure RCA No. 4}}}\)} & \multirow{  
In the next order, the statistical analysis of all data from Tables 3 and 4 was executed. Its results are summarized in Tables 5 and 6. The minimum value of \(V_{S}\) in the most cases was received from cross correlation method, whereas the maximum from zero crossing method. The average median value of \(V_{S}\) for specimens tested under \(p^{\prime}\) = 45 kPa is equal to 183.1 m/s, pure RCA, and 43% less, 104.5 m/s, composition of RCA with rubber chips. For specimens tested under \(p^{\prime}\) = 90 kPa, the median value for pure RCA is about 254.3 m/s and more than 50% less, 116.7 m/s, for its composition with rubber chips. A similar difference, namely 47%, is occurred for the average median values of \(V_{S}\) between specimens No 3 and 6 that are respectively 296.9 and 156.7 m/s. Analyzing other statistical parameters, e.g., dispersion of the results within a method, standard deviation, standard error and variance, the highest values were usually found for zero crossing interpretation method. Regardless of the type of a test material, it can be seen that this technique deviates significantly from others. A large spread of the results is characteristic as well for frequency domain method. It is higher, up to 93%, for composition of RCA with rubber chips than for pure RCA specimens. The smallest spread of the results provides peak-to-peak method, in the region of 1.1 m/s (specimen No. 5) to 4.7 m/s (specimen No. 4). For some specimens (No. 1 and 6) though, a small scatter of the results is obtained by cross correlation method, amounting to 7.5 and 2.8 m/s. After estimating standard error, it can be noticed that for most of the techniques of travel time identification in BEs testing standard error is minor, except for cross correlation. In general, it does not exceed the value of 1.3 m/s for pure anthropogenic material and 4.4 m/s for its modified version. The above-given data relates to frequency domain method. This means that the chosen interpretation methods are correct. The differences between empirical and theoretical values of \(V_{S}\) hardly exist. The average error in \(V_{S}\) calculation using one of the analyzed method deviates from the theoretical value of \(V_{S}\) by the standard error value (Tables 5 and 6). However, it should be remembered that presented errors do not exactly tell about the scale of the phenomenon.