# Numerical Assessment and Repair Method of Runway
## 3 Numerical Simulation (LS-DYNA M&S)
### Comparison and Discussion with Regard to the Results of Numerical Simulation  
At the field test, the damage on the concrete pavement was a small crater 30 cm in diameter and 78 cm in depth. In addition, as a result of the damage measurement conducted after the formation of the crater, cracks were generated along with 0-7 mm of upheaval on the concrete pavement due to the spread of the explosion pressure; a fracture zone was formed on the concrete slab up to an average diameter of 155.8 cm; and cracks were generated across the entire pavement. The numerical simulation result through the LS-DYNA program, under similar conditions, showed that the crater on the pavement surface had a diameter of 67.6 cm from the center; the depth of the damage was 67 cm including the upheaval on the pavement; and the displacement occurred throughout the base course. Furthermore, the height of the upheaval on the concrete pavement surface, caused by the impact of the explosion, was measured to be about 12 cm from the existing surface. The result of the computer simulation confirmed that a larger scale of damage occurred compared with the actual explosion test site, with a difference of around twice the diameter and 11 cm in the height of upheaval. The field test and M&S results are shown in Table 6.  
The computer simulation results presenting different results from the explosion test site suggest important causes as follows. First, an industrial explosive called MegaMEX, which has a speed of explosion at 6000 m/s, was used at the field blast test. Compared with the explosion speed of the explosive PBXN-109, which was applied in the simulation, the MegaMEX had a slower speed of explosion during the explosion test. As a result, the power of the explosion was smaller than the reality. Next, the TNT was mounted in a cylindrical tube and installed at the concrete boring part, since the design of an actual outer shell for the explosive was limited. As the shape of the tube was cylindrical and not spherical, small damage occurred on the pavement, caused by the pressure induced to the upper part of the tube. Finally, the modeling incorporated a high compression level by applying properties  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sort** & **Field Test** & **M\&S** \\ \hline Crater Diameter & 30 cm & 67.6 cm \\ Crater Depth & 78 cm & 55.2 cm \\ Damage layer & Separation Layer & Drainage Layer \\ Upheaval & 0–0.7 cm & 12 cm \\ \hline \hline \end{tabular}
\end{table}
Table 6: Comparison of the field test and M&S.  
Figure 7: Displacement curve.  
similar to the pavement surface, while for the field test the concrete properties of the cement stabilization layer was made with general concrete which has a low compression level. These causes and results confirm that it is necessary to utilize the field test results and numerical simulation results in a complementary manner. However, the recovery section is 1.8 m \(\times\) 1.8 m in size and about 84 cm in depth, meaning that some parts of the crushed stone and sand layer need to be repaired. For this reason, the damage repair sections which encompass the concrete pavement and the plastic deformation sections can produce similar results [26].