## 4 Results and Analysis
Then, Equation (12) can be obtained. Figure 4:6  
Then, Equation (13) can be obtained. Figure 4:7  
Substituting Equations (13) and (7) into Equation (5), Equation (14) can be obtained. Figure 4:8  
Added the static water pressure at the bottom of the pore, the total pore water pressure under vehicle load is shown in Equation (15). Figure 4:9  
where \(K\) is the bulk modulus of water, \(E\) is the elastic model of the asphalt mixture, \(\rho\) is the density of the water, \(r\) is the radius of the cylindrical pore and \(\xi\) refers to the range of water pressure on the side wall after the water pressure increases in the pores. According to the above calculation, when \(0<t<h/c\), the compression wave propagates upward from the bottom of the pore. In an ideal situation, the velocity of the water flow at the point where the compression wave is reduced to zero, and the water pressure increases by \(\Delta P\). When \(t=h/c\), the compression wave reaches the upper surface of the pore, the velocity of the whole water in the pore is reduced to zero and the water pressure at the bottom of the pore becomes maximum at \(P=\frac{\Delta v}{\left(1+\frac{2 kc}{2k}\right)}+\rho gh\). However, there is a pressure difference between the upper and lower ends of the wave at the upper surface of the pore, and the pressurized water in the pore moves upward at the velocity \(v\). At the time, an expansion wave is formed in the pore. When \(h/c<t<2h/c\), the expansion wave propagates from top to bottom, the pressure of the water flow at the point where the expansion wave is reduced by \(\Delta p\), and the water flow moves upward at the velocity \(v\). When \(t=2h/c\), the compression wave reaches the bottom of the pore, the whole free water in the pore finish the state of compression and the water pressure at the bottom of pore recovers to \(\rho gh\). At this time, the water flow is like a spring under pressure. After the external force is removed, the spring will not only return to its original length, but will also stretch because of inertia. Similarly, the water flow will continue to move upwards at the speed \(v\) due to inertia. Therefore, after the compression state is over, the water flow will not be stabilized in the static pressure state, but will be over-expanded and the pressure of water flow will continue to decrease. Until the pressure of water flow drops to \(-\Delta P\), the water at the bottom of the pore is stable, which in turn produces a new expansion wave. When \(2h/c<t<3h/c\), the new expansion wave propagates from bottom to top, the pressure of the water flow at the point where the new expansion wave reaches is reduced by \(\Delta p\), and the water flow at the point where the new expansion wave not reaches still moves upward at velocity \(v\). When \(t=3h/c\), the new expansion wave reaches the upper surface of the pore. At this time, the water pressure at the bottom of the pore becomes \(-\left(\frac{Kp}{\left(1+\frac{2K}{2c}\right)}-\rho gh\right)\), and the pressure difference between the upper and lower ends of the wave is \(\Delta P-\rho gh\), thus a new compression wave is generated in the pore. When \(3h/c<t<4h/c\), the new compression wave propagates from top to bottom, the pressure of the water flow at the point where the compression wave reaches recovers to \(P\), the water flow moves down at the velocity \(v\). When \(t=4h/c\), the new compression wave reaches the upper surface of the pore, and the water flow still moves towards the bottom of the pore at the velocity \(v\). Then, the pore water pressure circulates periodically, and the pore water pressure cycle is \(t=4h/c\). The above analysis is based on the assumption that the energy of the water flow in the pores is conserved, the pores are not connected with other pores, the permeability of the asphalt concrete material is zero, and there is no energy loss in the process. However, the actual situation is not the case.