# Dynamic Response Analysis of Airport Pavement under Impact Loading
## 5 Result and Analysis
Under the same tire pressures, the displacement at the top of the surface is 3.7% higher than that at the bottom of the surface, and the bottom of the base is 6.6% higher than that at the top of the soil foundation, which shows that the thickness of the layers and different structures have an effect on the displacement. Although the upper and lower surfaces of the same structure in different positions, the vertical displacement difference caused by the interlayer structure is significantly larger than the thickness of the structure. Figure 9: Effect of tire pressure on the impact performance of the airport pavement. (**a**) Effective stress. (**b**) Effective strain. (**c**) \(Z\)-displacement. As can be seen from Figure 10, when the tire pressure and sinking speed are certain, the maximum effective stress, effective strain, and vertical displacement of each structure slightly decrease with the increase in the landing pitch angle, and the maximum effective stress and strain also appear at the bottom of the surface and at top of the soil foundation, but the degree of influence of the landing pitch angle is very limited. It is proven that this parameter mainly ensures the attitude stability of the aircraft during takeoff and landing, and prevents the phenomenon of aircraft tail grazing the ground and loss of control due to stall speed. From Figure 11, it can be seen that the maximum effective stress, effective strain, and vertical displacement of each structure increased with the increase in the sinking speed at a certain tire pressure and landing pitch angle. Figure 11a displays the effect of sinking speed on the maximum effective stress of the airport pavement. At 3.0 m/s, the maximum flexural tensile stress at the bottom of the surface is 9.9% and 25.2% higher than at 2.0 m/s and 1.0 m/s, respectively, and the time required to reach the maximum stress is 0.012 s and 0.025 s earlier, implying that the magnitude of the sinking speed affects the impact loading when the landing gear is in contact with the pavement. Therefore, the sinking speed during the landing process should be controlled to ensure the structural safety of the pavement. Figure 11b demonstrates the maximum effective strain of the pavement for different sinking speeds. It can be seen from the figure that the maximum strain at the top of the soil foundation at 3.0 m/s increased by 31.7% and 93.1% compared to 2.0 m/s and 1.0 m/s, respectively, demonstrating that the increase in sinking speed significantly increases the strain on the airport pavement and affects the safety. Figure 11c reveals the vertical displacement changes of each structure during the aircraft impact process, and the law is similar to the influence of tire pressure on vertical displacement. Compared to 2.0 m/s and 1.0 m/s, the maximum vertical displacement of 3.0 m/s increased by 28.1% and 93.1%, respectively. However, in terms of time, it can be clearly seen that increasing the sinking speed significantly accelerates the time when the pavement displacement reaches the maximum value. The average time to reach the maximum displacement of  
Figure 11: Effect of sinking rate on the impact performance of airport pavement. (**a**) Effective stress. (**b**) Effective strain. (**c**) Z-displacement. Figure 10: Effect of landing pitch angle on the impact performance of airport pavement. (**a**) Effective stress. (**b**) Effective strain. (**c**) Z-displacement. each structure at the sinking speed of 3.0 m/s, 2.0 m/s and 1.0 m/s is 0.013 s, 0.014 s, and 0.018 s, respectively, indicating that the larger the sinking speed, the larger the displacement deformation of the pavement in a shorter time. In addition to the above rules, for a given tire pressure, the landing angle and sinking speed of the aircraft tire are constant. The equivalent stress at the bottom of the surface is the largest, followed by the top of the surface, the bottom of the base, the top of the soil foundation, and the bottom of the soil foundation.