## 1 Introduction  
Geosynthetics have been widely used as a reinforcement material in geotechnical structures, such as roadways, railways, steep slopes, embankments and retaining walls, with the function of improving the mechanical behavior of the surrounding soils or aggregates [1; 2; 3]. Several benefits, including the reliability, cost-effectiveness and contribution towards sustainability have led to the increasing use of geosynthetics in civil infrastructure projects worldwide. In particular, the role of geosynthetics in sustainable infrastructure development and circular economy has been well recognized and highlighted in recent years. For instance, these materials facilitate energy and resource savings by accelerating the construction process, minimizing on-site excavation, reducing the need to transport bulky materials, extending infrastructure longevity and decreasing maintenance requirements. They can replace or reduce the use of other construction materials, such as sand and aggregates, thus attenuating the adverse environmental impacts from natural resource extraction. In addition, they often enable the use of locally available low-quality soils (such as cohesive soils) or recycled aggregates (e.g., construction and demolition waste) as alternative fill materials, in which case they significantly contribute towards reducing the amount of waste directed to landfills [4]. The geosynthetic reinforcement mechanism is mainly dependent upon the interaction developed at the soil-geosynthetic interfaces. The interaction between the soil and reinforcement redistributes stresses within the soil mass, increasing the stability of the reinforced structure, and decreasing horizontal deformations. These redistributions of stress within the reinforced soil depend on the soil properties, the reinforcement characteristics, and the interaction between components. It is essential to identify the interaction mechanism and the most suitable test for its characterization [5]. Various experimental techniques have been developed to enhance the comprehension of the interaction between soils and geosynthetics. Among these methods are the direct shear test, pullout test, in-soil tensile test and ramp test. From these, the direct shear and pullout tests stand out as the most frequently used. The direct shear test assesses the interaction at the interface when the soil mass slides on the surface of the reinforcement. In contrast, the pullout test is applicable when the reinforcement is pulled out from the soil mass [6]. In the past several decades, different researchers have analyzed the interface mechanism between the geosynthetic and surrounding soil. Direct shear interface tests have been investigated by the authors of [5; 7; 8]. The pullout response has been studied experimentally by considering various influential factors such as box and specimen size, sleeve length, active length, test speed, soil characteristics and geosynthetic properties [9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19], as well as using analytical and numerical methods [20; 21; 22; 23]. Apart from high-quality (i.e., granular) soils, the pullout behavior of geosynthetics in alternative backfill materials, such as cohesive and residual soils or recycled aggregates, has also been the subject of significant research [23; 24; 25; 26]. In some structures, the geosynthetic reinforced soil is exposed to repeated or cyclic loads, which may be induced by compaction, road or railway traffic, wave loading and earthquakes. The understanding of the cyclic behavior of such reinforced soil structures is crucial for the design and performance. Reports of soil-geosynthetic interaction under cyclic loading conditions are available in [27; 28; 29; 30; 31; 32; 33; 34; 35].