## 1 Introduction  
Asphalt pavement presents diverse dynamic responses to vehicle loading in dry and saturated conditions. When surface runoff exists on the surface layer of roads, pore water pressure with positive and negative alternations will be generated by continuous interaction between vehicle wheels and water, which deteriorates service environments for asphalt pavement and gradually causes moisture damage [1]. Characterizing the dynamic responses of asphalt pavement is of great importance and can help to better understand the damage mechanism induced by dynamic pore water pressure and to improve relevant design methods for asphalt pavement with better service performance and long service life. Numerical simulation is a useful and convenient method to deeply explore the dynamic responses inside asphalt pavement in dry and saturated conditions, especially for those which may cost a lot and are not easily obtained from field measurements. Great efforts have been made to evaluate the dynamic responses in dry and saturated asphalt pavement based on numerical simulation. [PERSON] et al. [2] evaluated the influence of saturation on the base course of permeable pavement with a novel polyurethane binder using the methods of numerical simulation and a full-scale field test, while a great influence of water content was found on the hydromechanical properties of asphalt pavement. [PERSON] et al. [3] numerically investigated the comprehensive influence of moisture diffusion and mechanical loading on the dynamic responses of flexible pavements. They found that moisture diffusion had a significant impact on the micromechanical response of asphalt layers, especially during the initial service months. [PERSON] [4] analyzed the impact of excess water on the structural performance of flexible pavements using a 2D finite element model (FEM), in which both transient unsaturated flow and porous nonlinear behavior of foundations were taken into account. [PERSON] et al. [5] constructed a 3D FEM model to discuss the dynamic response characteristics of saturated asphalt pavement under multifield coupling, and it was found that damage to the asphalt membrane is mainly caused by the cyclic effect of positive and negative pore water pressure. [PERSON] et al. [6] applied a discrete element model to simulate the mechanical response of asphalt surfaces under moving traffic loads, and the factors of temperature gradient and fatigue damage could be taken into account simultaneously. In order to evaluate the influence of water on the dynamic responses of asphalt pavement, accurately determining the detailed values of dynamic pore water pressure is necessary. [PERSON] et al. [7] evaluated pore water pressure at the bottom of the upper layer with a vehicle speed of 60 km/h, and the positive magnitude was calculated at 332.2 kPa. [PERSON] et al. [8] obtained pore water pressure of less than 14 kPa on the top of the base layer with a vehicle speed of 60 km/h. [PERSON] et al. [9] assessed pore water pressure of 60 kPa in the midpoint of the upper layer with a vehicle of 40 km/h. [PERSON] and [PERSON] [10] calculated the value of pore water pressure, which could reach more than 2.5 MPa. It could be found that numerical values of pore water pressure obtained from different research studies were diverse, which might be induced by the differences in the adopted FEM models. Furthermore, inevitable differences also existed between numerical models and actual asphalt pavement with complicated structures and service environments. In this case, building an FEM model based on the actual conditions of asphalt pavement is necessary, and relevant field measurements should also be subsequently conducted to monitor dynamic responses to calibrate and validate the FEM model. Cooperating with field tests, the characteristics of the structural dynamic responses obtained from numerical simulation can thus be meaningful and reliable. A validated FEM model can further lay solid foundations for following systematic field tests.