## 4 Summary of Results and Discussion
### Dynamic Deformation of Ice Samples at Moderate Rates
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Temperature** & **Sample** & \begin{tabular}{c} **Nominal** \\ **Strain-Rate** \\ **(s\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **Sustaining** \\ **Time (ms)** \\ \end{tabular} & \begin{tabular}{c} **Average True** \\ **Strain-Rate** \\ **(s\({}^{-1}\))** \\ \end{tabular} & \
\begin{tabular}{c} **Nominal** \\ **Ultimate \\ **Strain (\%)** \\ \end{tabular} &
\begin{tabular}{c} **True** \\ **Ultimate** \\ **Strain (\%)** \\ \end{tabular} \\ \hline \multirow{6}{*}{\(-5\)} & SH01 mps4 & 2 & 4.51 & 0.44 & 0.90 & 1.98 \\  & SH02 mps3 & 4 & 2.36 & 1.09 & 0.94 & 2.57 \\  & SH01 mps2 & 10 & 0.84 & 2.79 & 0.84 & 2.34 \\  & SH1 mps2 & 20 & 0.23 & 5.78 & 0.46 & 1.33 \\  & SH2 mps3 & 40 & 0.16 & 9.16 & 0.64 & 1.47 \\  & SV01 mps3 & 2 & 5.50 & 0.56 & 1.10 & 3.08 \\  & SV02 mps3 & 4 & 2.35 & 0.89 & 0.94 & 2.09 \\  & SV05 mps2 & 10 & 1.21 & 2.73 & 1.21 & 3.30 \\  & SV1 mps2 & 20 & 0.20 & 4.31 & 0.40 & 0.86 \\  & SV2 mps3 & 40 & 0.11 & 9.35 & 0.44 & 1.03 \\ \hline \multirow{6}{*}{\(-10\)} & SH01 mps5 & 2 & 6.19 & 0.41 & 1.24 & 2.54 \\  & SH02 mps3 & 4 & 2.80 & 0.88 & 1.12 & 2.46 \\  & SH05 mps2 & 10 & 0.97 & 2.27 & 0.97 & 2.20 \\  & SH1 mps3 & 20 & 0.41 & 5.46 & 0.82 & 2.24 \\  & SH2 mps2 & 40 & 0.12 & 9.15 & 0.48 & 1.10 \\  & SV01 mps2 & 2 & 6.03 & 0.48 & 1.21 & 2.89 \\  & SV02 mps2 & 4 & 2.24 & 1.14 & 0.90 & 2.55 \\  & SV05 mps3 & 10 & 1.26 & 2.01 & 1.26 & 2.53 \\  & SV1 mps3 & 20 & 0.28 & 5.98 & 0.56 & 1.67 \\  & SV2 mps3 & 40 & 0.15 & 9.53 & 0.60 & 1.43 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Ultimate strain and strain-rate results of soft ice derived from actuator displacement and DSCM. SH denotes soft ice sample loaded in the horizontal direction, SV denotes soft ice sample loaded in the vertical direction. compression experiments. The nominal strain-rate chosen in the present study is in the range of 2-40 s\({}^{-1}\), while the true strain rate is in the range of 0.4-10.0 s\({}^{-1}\). Relationship between Compressive Strength and Strain-Rate, Air Porosity, Loading Direction as Well as Temperature in Moderate Strain-Rate Range  
By means of DSCM, the true strain-rate can be obtained. Results of uniaxial compressive strength versus true strain-rate are shown in Figure 17. The uniaxial compressive strength results show huge scatter and it is more serious in soft ice. As many previous studies have reported, huge scatter may be due to internal structure differences between ice specimens and imperfect interfaces between platen and ice surface. In the present work, ice grain size varies 2.0-7.0 mm in diameter based on measurement results of some samples. As not all of the grain sizes of specimens are measured, we cannot relate the difference in strength to grain size quantitatively. However, it has been well confirmed that ice with smaller grain size trends to obtain a greater strength value [16]. The grain size difference in experimental specimens could be a significant reason for the huge scatter. In soft ice, besides the difference in grain sizes, the difference in air bubbles contained in different ice specimens is also a factor in making ice strength scattered. Therefore, strength data of soft ice show greater scatter than that of hard ice. In addition, it is difficult to ensure perfect interface between platen and ice surface though ice specimens are finely machined. Loading direction seems to have little effect on strength scatter. Though a significant scatter exists in strength data, it does not evidently affect us analyzing the relationships between compressive strength and strain-rate, air porosity, loading direction as well as temperature. Two kinds of ice with different air porosities are used in experiments: hard ice with an average air porosity of 0.1% and soft ice with an average air porosity of 2.0%. In the strain-rate range of 0.4-10.0 s\({}^{-1}\), at \(-5\)\({}^{\circ}\)C, for hard ice, the average horizontal and vertical compressive strength are 4.0 MPa and 5.0 MPa, respectively.