# Study of Static and Dynamic Properties of Sand under Low Stress Compression
## 3 Results
### The Results of AE Measurements
#### 3.3.10 Summary of AE Results  
Table 1 demonstrates the comparison of the sensitivity of different parameters to a stress increase. The symbols +, -, +/- and -/+ in Table 1 imply that a parameter is sensitive to a stress level increase, insensitive to a stress level increase, more sensitive than insensitive (it was found to be sensitive in the majority of the tests) and more insensitive than sensitive (it was found to be insensitive in the majority of the tests), respectively. Analysis of Table 1 indicated that the parameters which were the most sensitive to stress increases were the AE hit number and absolute energy (both average and cumulative), while the energy and rise time were also sensitive but only for the dry sand samples. Regarding the other six parameters, it was seen that their cumulative changes were probably due to their dependence on the number of AE hits.  
Figure 14: The stress–strain relationships (solid curves) vs. the values of the peak number (PCNTs) for the OD (blue), UCD (green) and UCW (red) tests. The empty squares and the full circles denote the values of the average (index = LS) and cumulative (index = cum) PCNTs for a load stage, respectively. Panels (**a–d**) present the results for natural dune sand and its three extracted fractions: 2.36–0.6, 0.6–0.3 and 0.3–0.075 mm, respectively. Note that in the used number format, the notation “E\(\pm\)xx” is part of a scientific notation and corresponds to “\(\cdot 10^{\pm xx}\)”.  
Figure 15: The stress–strain relationships (solid curves) vs. the values of the absolute energy (AbsEnergy) for the OD (blue), UCD (green) and UCW (red) tests. The empty squares and the full circles denote the values of the average (index = LS) and cumulative (index = cum) AbsEnergy for a loading stage, respectively. Panels (**a–d**) show the results for natural dune sand and its three extracted fractions: 2.36–0.6, 0.6–0.3 and 0.3–0.075 mm, respectively. Note that in the used number format, the notation “E\(\pm\)xx” is part of a scientific notation and corresponds to “.10\({}^{\pm xx}\)”.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{3}{c}{**Average Value of the Parameter**} & \multicolumn{3}{c}{**Cumulative Value of the Parameter**} \\  & \multicolumn{3}{c}{**for a Loading Stage**} & \multicolumn{3}{c}{**for a Loading Stage**} \\  & \multicolumn{3}{c}{**(Sensitivity to Stress Level)**} & \multicolumn{3}{c}{**(Sensitivity to Stress Level)**} \\ \hline  & OD & UCD & UCW & OD & UCD & UCW \\ \hline AE hit number & + & + & + & + & + & + \\ Rise time & + & + & -/+ & + & + & -/+ \\ Counts & - & -/+ & -/+ & + & + & -/+ \\ Energy & + & + & +/- & + & + & +/- \\ Duration & - & - & - & + & + & +/- \\ Amplitude & - & - & - & + & + & +/- \\ Average & + & - & - & + & + & -/+ \\ frequency & - & -/+ & - & + & + & +/- \\ Peak number & - & -/+ & - & + & + & +/- \\ Absolute energy & + & + & +/- & + & + & +/- \\ \hline \hline \end{tabular}
\end{table}
Table 1: Summary of AE measurement results. For the interpretations of the +, -, +/- and -/+ symbols, refer to the main text.