## 5 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Moisture Content of the Sility Sand Sample m/\(y\)**} \\  & \multicolumn{6}{c}{**Difference between \(f_{\text{slitC1,3,4}}\) (\(f_{\text{slitC1,3,4}}\)) and Reference \(f_{\text{slitC2,3}}\) (\(f_{\text{slitC1,3}}\))**} \\ \cline{2-7}
**Leuncher** & & & **\(\Delta\)** & \(\Delta\)** & \(\Delta\)** \\
**Pressure p/\(p\)** & \(\omega_{1}=0\%\) & \(f_{\text{slitC1,3,4}}\) & \(\omega_{2}=9\%\) & \(f_{\text{slitC1,4}}\) & \(\omega_{3}=10\%\) & \(f_{\text{slitC1,3,4}}\) & \(\omega_{4}=15\%\) & \(f_{\text{slitC1,3,4}}\) \\
**Velocity v\({}_{\text{l}}\)** & & \(f_{\text{slitC1,3}}\) & & \(f_{\text{slitC1,3}}\) & & \(f_{\text{slitC1,3,4}}\) & \\ \hline \(P_{1}=1.2\) bar & \(f_{\text{slitC1,3,4}}=16.64\%\) & 1.50\% & \(f_{\text{slitC1,3,4}}=18.17\%\) & 3.03\% & \(f_{\text{slitC1,3,4}}=17.15\%\) & 2.01\% & \(f_{\text{slitC1,3,4}}=16.66\%\) & 1.52\% \\ \(P_{2}=1.8\) bar & \(f_{\text{slitC1,3,4}}=23.58\%\) & 8.44\% & \(f_{\text{slitC1,3,4}}=23.97\%\) & 8.83\% & \(f_{\text{slitC1,3,4}}=17.15\%\) & 2.08\% & 6.94\% & \(f_{\text{slitC1,3,4}}=19.92\%\) & 4.78\% \\ \(P_{3}=2.4\) bar & \(f_{\text{slitC1,3,4}}=23.50\%\) & 9.96\% & \(f_{\text{slitC1,3,4}}=26.22\%\) & 11.08\% & \(f_{\text{slitC1,3,4}}=22.96\%\) & 7.82\% & \(f_{\text{slitC1,3,4}}=21.24\%\) & 6.10\% \\ \(P_{3}=2.4\) bar & & & \(\Delta\) & & & & \\  & & \(f_{\text{slitC1,3,4}}\) & & \(f_{\text{slitC1,3,4}}\) & & \(f_{\text{slitC1,3,4}}=4\) & & \(f_{\text{slitC1,3,4}}=f_{\text{slitC1,3,4}}\) & \(f_{\text{slitC1,3,4}}=24.24\%\) \\  & & \(f_{\text{slitC1,3,4}}\) & & \(f_{\text{slitC1,3,4}}\) & & \(f_{\text{slitC1,3,4}}=25.79\%\) & 5.31\% & \(f_{\text{slitC1,3,4}}=25.30\%\) & \(f_{\text{slitC1,3,4}}=4.87\%\) \\ \hline \(P_{1}=1.2\) bar & \(f_{\text{slitC1,3,4}}=24.80\%\) & 4.32\% & \(f_{\text{slitC1,3,4}}=28.71\%\) & 8.23\% & \(f_{\text{slitC1,3,4}}=0.70\%\) & \(f_{\text{slitC1,3,4}}=20.84\%\) & 0.36\% \\ \(P_{2}=1.8\) bar & \(f_{\text{slitC1,3,4}}=29.17\%\) & 8.69\% & \(f_{\text{slitC1,3,4}}=31.00\%\) & 10.52\% & \(f_{\text{slitC1,3,4}}=31.01\%\) & 4.51\% & \(f_{\text{slitC1,3,4}}=24.76\%\) & 4.28\% \\ \(P_{3}=2.4\) bar & & & & & & & \\ \(P_{3}=21.32\) m/s & \(f_{\text{slitC1,3,4}}=32.87\%\) & 12.39\% & \(f_{\text{slitC1,3,4}}=35.65\%\) & 15.17\% & \(f_{\text{slitC1,3,4}}=25.0\%\) & 5.31\% & \(f_{\text{slitC1,3,4}}=32.30\%\) & 4.87\% \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Summary of percentage changes in slit and clay fraction as a consequence of bar projectile impact during SHPB testing compared to the \(f_{\text{slitC1}}\) reference sample depending on the configuration of variables—moisture content of the soil sample \(v_{\text{l}}\) and initial impact pressure \(p\). The four directions of behavioral trends in the dynamic characteristics of the silty sand discussed above are susceptible to the influence of experimental conditions. Special attention should be given to the issues:  
* Parallelism of the contact surface between the soil sample-initiating bar and the transmitting bar. There is a particular risk of the parallelism condition not being achieved as a result of the compaction process of the soil sample. Silty sand is a loose material and susceptible to shape change. Applying the pressure plate elements in a way that is not perpendicular to the wall edge of the soil sample casing (rigid ring) will result in non-parallelism of the contact surface between the soil sample-initiating bar and transmitting bar (i.e., there will be a local air void). Consequently, incorrect waveform data will be recorded for the reflected wave (as a result of non-parallelism of the contact surface between soil sample-initiating bar) and transmitted wave (as a result of non-parallelism of the contact surface between the soil sample-transmitting bar). * Cohesive effect resulting from the internal structure of the tested soil sample. Silty sand is not a pure representative of sand containing only grains with a diameter in the range of 0.063 mm-2 mm (according to Figure 1).