## 3 Results
### Specific Impulse Distribution  
Figure 6 plots the average specific impulse for each test in each series as a function of radial distance. The shaded region indicates the standard error on the mean within a given test (based on the four measurements for each radius and one for the central bar). It can be seen that there is a good test to test the consistency for measurements at radii of 25 mm and above. The variation in the loading at the central measurement point is to be expected as there is a single measurement point that is highly sensitive to small variations in the charge position. Figure 6a,c,e show the effect of increasing moisture content on the pressure distributions. As expected, at low moisture contents, there is no phenomenological difference in the distributions and the increase in total impulse (from the integrated signals discussed later) shows a minimal increase with increasing moisture content. Figure 6a,b show the specific impulse distributions for the carbonate and LB tests at the same moisture contents. LB has historically been identified as a soil which generated very repeatable loading [11] (especially in comparison with well-graded soils). The carbonate test results show a tighter spread on impulse distributions, thus making this an exceptionally repeatable test condition. The impact of this will be discussed later in the total impulse calculations.  
Figure 5: Particle size distribution of quartz (LB) and carbonate sand before and after blast testing using sieve analysis.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Sand**} & \multicolumn{2}{c}{**Pre**} & \multicolumn{2}{c}{**Post**} & \multicolumn{2}{c}{**\(\mathbf{B_{t}}\)**} \\  & \(\mathbf{D_{10}}\) & \(\mathbf{D_{50}}\) & \(\mathbf{C_{u}}\) & \(\mathbf{D_{10}}\) & \(\mathbf{D_{50}}\) & \(\mathbf{C_{u}}\) & **Total Breakage** \\ \hline Quartz & 0.686 & 0.970 & 1.494 & 0.440 & 0.938 & 2.264 & 7.3\% \\ Carbonate & 0.491 & 0.742 & 1.672 & 0.335 & 0.734 & 2.433 & 4.2\% \\ \hline \end{tabular}
\end{table}
Table 3: Summary of particle size distribution parameters for both soil types before and after testing, all values in mm unless otherwise specified.  
Figure 6: Specific impulse distribution for the five series considered; each plot shows the results for the repeat tests within the given series and demonstrates the repeatability of the data. (**a**) Carbonate at 2.5% moisture content; (**b**) quartz at 2.5% moisture content; (**c**) carbonate at 5.0% moisture content; (**d**) quartz at 5.0% moisture content; (**e**) carbonate at 7.5% moisture content.  
Figure 7 plots the specific impulse as a function of radial distance averaged across all measurement points in a given series (i.e., the average of the results from multiple measurement points in all the nominally identical tests shown in Figure 6). It can be seen in Figure 7a that, as the moisture content of the carbonate sand increases, there is a small increase in the measured loading. This is in agreement with the results of [PERSON] et al. [17], who investigated the effects of moisture content in quartz-based sands. Figure 7b,c show that both the magnitude and spatial distribution of the loading for carbonate and quartz sand is comparable and, again, highlights the level of repeatability achievable with careful control over the soil preparation.