## 4 Simulation Results
### Impact of the Thickness of a Fragile Wall  
Blast pressure will be leaked outside the ammunition depot through cracks in the wall, as created under blast pressure. In the UFC3-340-02 Specification, this effect is directly deemed as a vent opening, and the blast pressure absorbed by the thickness of the wall upon cracking is ignored. In this study, 1 pound of TNT was placed 10 cm from a 3000 psi concrete wall with a blast height of 10 cm and wall thicknesses of 3 cm, 5 cm, and 7 cm, and the erosion condition of the concrete was the maximum shear strain of 0.004. The simulation results are shown in Table 13 and Figure 25. The vent opening is small and leakage pressure is low when the wall is 3 cm thick; the vent opening is smaller and leakage pressure is lower when the wall is 7 cm thick, indicating that the wall thickness has an impact on vent opening size, and hence has a great impact on leakage pressure. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**1-Pound TNT-20 \(\times\) 20 cm Vent Opening Model (Blast Height 20 cm)**} \\ \cline{2-7}
**Distance** & \multicolumn{4}{c}{**Observation Point Height**} \\ \cline{2-7}
**from Blast** & \multicolumn{2}{c}{**10 cm**} & \multicolumn{2}{c}{**20 cm**} & \multicolumn{2}{c}{**30 cm**} \\ \cline{2-7}
**Point** & \multicolumn{2}{c}{**Blast Pressure Bar**} & \multicolumn{2}{c}{**Impulse Bar, ms**} & \multicolumn{2}{c}{**Blast Pressure Bar**} & \multicolumn{2}{c}{**Impulse Bar**} & \multicolumn{2}{c}{**Impulse Bar**} \\ \hline
30 cm & 37.5 & 0.886 & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\
40 cm & 23.5 & 0.588 & 12.7 & 0.460 & 3.65 & 1.100 \\
50 cm & 26.7 & 1.990 & 9.9 & 0.650 & 4.18 & 0.862 \\
60 cm & 20.1 & 1.140 & 11.2 & 0.807 & 4.86 & 0.891 \\
70 cm & 13.7 & 1.130 & 9.6 & 0.839 & 6.27 & 0.895 \\
80 cm & 10.4 & 1.220 & 7.76 & 1.270 & 5.58 & 1.020 \\
90 cm & 7.74 & 1.250 & 6.38 & 1.180 & 4.86 & 0.932 \\ \hline \hline \multicolumn{7}{c}{**Center of the side wall of the ammunition depot**} & \multicolumn{2}{c}{**Center of the back wall of the ammunition depot**} & \multicolumn{2}{c}{**Center of the roof of the ammunition depot**} \\ \hline Blast & Impulse bar, ms & Blast pressure bar & Impulse bar, ms & Blast pressure bar & Impulse bar, ms \\ \hline
173 & 43.127 & 115 & 42.364 & 58.8 & 11.476 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Blast pressure and impulse of 20 \(\times\) 20 cm vent opening at the blast height of 20 cm. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{5}{c}{**1-Pound TNT Blast Point 10 cm from 3000 psi Concrete Wall, Blast Height 10 cm Unit: Bar**} \\ \hline \hline \multicolumn{5}{c}{**Wall thickness 3 cm**} \\ \hline \hline \multicolumn{5}{c}{**Distance behind the**} & **Measurement height** & **Measurement height** & **Measurement height** \\
**wall** & **10 cm** & **20 cm** & **30 cm** \\ \hline \(7\) cm & 5.27 & 2.93 & 4.95 \\ \(17\) cm & 3.93 & 2.88 & 3.31 \\ \(27\) cm & 1.38 & 1.21 & 1.09 \\ \hline \multicolumn{5}{c}{**Wall thickness 5 cm**} \\ \hline \hline \multicolumn{5}{c}{**Distance behind the**} & **Measurement height** & **Measurement height** & **Measurement height** \\
**wall** & **10 cm** & **20 cm** & **30 cm** \\ \hline \(5\) cm & 7.84 & 3.2 & 1.88 \\ \(15\) cm & 5.71 & 3.58 & 3.81 \\ \(25\) cm & 2.85 & 1.41 & 0.88 \\ \hline \multicolumn{5}{c}{**Wall thickness 7 cm**} \\ \hline \hline \multicolumn{5}{c}{**Distance behind the**} & **Measurement height** & **Measurement height** & **Measurement height** \\
**wall** & **10 cm** & **20 cm** & **30 cm** \\ \hline \(3\) cm & 2.91 & 1.2 & 1.22 \\ \(13\) cm & 3.33 & 1.98 & 1.32 \\ \(23\) cm & 1.26 & 0.78 & 0.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Impact of wall thickness on leakage pressure.