## 1 Introduction  
In China's southern coastal region, which sees summer rainstorms (before rainstorms where the asphalt pavement temperature can be up to 60 \({}^{\circ}\)C or more), for a short period, rainstorms bring the high-temperature asphalt pavement down to 30 \({}^{\circ}\)C or less. The asphalt pavement experiences rapid warming and drying in the intervening rainstorms; cooling-warming and drying-rainfall cooling (dry and wet cycle) form the sizeable wet temperature cycle environment in which the asphalt mixture exists. In a sizeable wet temperature cycle environment, the asphalt mixture's internal temperature drops due to the sharp contraction and produces micro-cracks [1, 2]. The infiltration of rainwater along the cracks further aggravates the decay of the mechanical properties of the asphalt mixture [3]. Although modifiers, fibers, rubber, and other additives can be used to improve the effectiveness of asphal mixtures in terms of their resistance to the wet temperature cycle [4; 5], early-stage damage such as severe water damage and cracking [6] still occurs in asphalt pavements in the region [7; 8]. Therefore, it is of great significance to analyze the decay law of the mechanical properties of asphalt mixtures under the action of a sizeable wet temperature cycle for the design of asphalt pavements in high-temperature and rainstorm-prone areas in summer and to reduce the early-stage damage caused by the temperature and humidity changes in the asphalt pavements in this area. To research the effect of temperature and humidity on the properties of asphalt mixtures, [PERSON] et al. [9] and [PERSON] et al. [10] used the AASHTO T182 test method, in which mixture specimens are submerged in water and immersed for different times at target temperatures in order to simulate the effect of wet temperature coupling. However, this method is mainly used to evaluate the water stability of asphalt mixtures and does not consider the influence of the change in temperature and humidity conditions and cyclic action; based on the high-temperature water immersion test, [PERSON] et al. [11] and [PERSON] et al. [12] adopted high-temperature water immersion and subjected asphalt mixtures to drying cycle treatment to simulate high-temperature and high-humidity conditions. The cycle's effect on the performance of the asphalt mixture found an excellent linear relationship between the number of wet and dry cycles and the stability decay rate. However, in the wet and dry cycle and sizeable wet temperature cycle under the conditions of the asphalt mixture performance degradation mechanism, there was a big difference between the former and the latter; based on the small amplitude of temperature and humidity, the former was based on reduced asphalt aggregate adhesion caused by small changes in temperature and humidity, while the latter focused on the sharp contraction of asphalt mixtures caused by the sudden drop in temperature from heavy rainfall under high-temperature conditions [13; 14; 15]. The use of a particular freeze-thaw cycle (AASHTO T 165) test with different freezing and thawing durations has been reported in the literature, and it has been found that the freeze-thaw cycle can affect the splitting strength, compressive strength, and resilience modulus of the asphalt mixture to different degrees. However, the freeze-thaw cycle method is mainly aimed at areas with a lower average annual temperature; the temperature difference between day and night is significant, and areas with a large amount of asphalt pavement in the natural environment, such as the north of China, most frequently experience the freezing and thawing. In the south of China, the summer high-temperature rainstorms do not align with the region in terms of climatic characteristics.