## 1 Introduction  
For the maintenance of old roads or the reconstruction and upgrading of low-grade highways, the commonly adopted method is to overlay the asphalt pavement layer. Under the action of load and environment, the asphalt pavement layer will fill in the original old pavement joints and cracks at the occurrence of the stress concentration phenomenon, so that the asphalt pavement layer produces the bottom-up cracks-reflection cracks [1; 2]. Reflective cracking can cause damage such as cracking and loosening, which significantly reduces the performance and service life of the pavement. To mitigate and prevent reflective cracking, stress-absorbing layer technology has been developed [3; 4]. This technology involves adding a layer of material that can absorb the stress and strain caused by the movement of the old pavement, thus delaying or avoiding the formation of reflective cracks [5; 6]. A stress-absorbing membrane interlayer is a type of interlayer material that is placed between the asphalt surface layer and the original old pavement or semi-rigid base. Its main function is to absorb or reduce the stress concentration that occurs at the joints or cracks of the old pavement, and to decrease the load stress and temperature stress at the bottom of the asphalt surface layer. This can slow down the initiation and expansion of reflective cracks, and effectively improve the service life of the asphalt surface layer [5; 6]. The common materials for stress-absorbing layers are crumb-rubber-modified asphalt [7], geotextile [8], and smart composite [9]. Among them, crumb-rubber-modified asphalt has been widely used due to its excellent performance and sustainability [3]. [PERSON] [10; 11] and [PERSON] [7] examined the reflection cracking resistance performance of a stress-absorbing membrane interlayer (SAMI) under traffic load and found that the SAMI can significantly delay reflective cracking. [PERSON] [12] studied the reflection cracking resistance performance of six kinds of asphalt overlays by bending and shear tests. The results show that SAMPAVE (Stress Absorbing Mixtures Pavement), a stress absorbing mixture developed by Chang'an University, has excellent anti-cracking performance for fatigue. [PERSON] [13] studied the crack resistance of warm mix rubber-modified asphalt mixture (WMRMA) by tensile stress restrained specimen test (TSRST) and finite element analysis method. The results show that WMRMA shows good low-temperature performance in the case of blending and compaction temperature fall of 30 \({}^{\circ}\)C, and it can delay the formation and extension of reflective cracks on the asphalt surface and prolong the service life of the asphalt surface. [PERSON] [14] developed a 3D finite element model to simulate the load response of inverted pavement with two types of interlayers: aggregate interlayer and stress-absorbing membrane interlayer. The results showed that the asphalt concrete layer of stress-absorbing membrane interlayer pavement experienced lower stress and strain levels than that of aggregate interlayer pavement. [PERSON] [15] conducted the Hamburg wheel tracking test on four stress-absorbing interlayers, and the results showed that the asphalt-rubber sand concrete interlayer had the best reflection crack resistance performance. [PERSON] [16] conducted an experimental study on the influence of temperature, frequency, and geocomposite strength on the asphalt overlay cracking. The results revealed that temperature was the most significant factor in the reflective cracking rate. [PERSON] [17] examined the performance of natural zeolite and hydrated lime as additives for crumb-rubber-modified asphalt binder to prevent reflective cracking in composite pavements. The results show that both additives reduced the crack propagation rate, but natural zeolite was more effective than hydrated lime. [PERSON] [18] tested three kinds of warm mix rubber asphalt with different gradations and found that the gradation had a significant effect on the performance.