## 1 Introduction  
Iron tailings are one of the products of iron ore sorting operations. The stacking of tailings not only affects the surrounding environment, but also seriously threatens the lives and property security of the people in the lower reaches of the reservoir area. Therefore, how to use those iron tailings to turn waste into treasure is an effective means to reduce the dam-break risk of an iron tailings reservoir. Much research has been carried out on the resource utilization of iron tailings powder, including concrete fine aggregate [1], sewage treatment [2], filling material of composite material [3], recovered iron ore [4], and as a road material [5]. Lizhu Iron Mine is located in Shaoxing city, Zhejiang province, China. It produces about 200,000 tons of dewatered tailings every year and accumulates more than 20 million tons of tailings in the existing tailings dam yard. The iron tailings mainly contain tailings with a particle diameter of less than 0.075 mm, which are cohesionless, non physicochemically active, and difficult to utilize. Certain means shall be taken to improve its resource utilization. Adding fiber to soil can improve the mechanical properties of soil through the tensile properties of fiber and the interfacial strength between fiber and soil [6; 7; 8; 9]. [PERSON] et al., [PERSON] et al., and [PERSON] studied the mechanical properties and test methods of fiber-reinforced sand, such as interfacial characteristics, constitutive model, shear modulus, and damping ratio, through triaxial tests and a resonance columns test [10; 11; 12; 13]. [PERSON] proposed a constitutive model of fiber-reinforced clay and concluded that fiber reinforcement can effectively improve the undrained shear strength of soil [14]. [PERSON] conducted the comparative study on two kinds of fiber-reinforced clay sample production methods of \"impact\" and \"kneading\" through an unconsolidated undrained triaxial test [15]. [PERSON] et al. studied the effects of fiber width, fiber dosage, and fiber length on the swelling properties of expansive soils [16]. Taking the effects of fiber dosage, fiber length, relative compactness, and confining pressure into consideration, [PERSON] et al. carried out a series of cyclic triaxial tests on unreinforced and reinforced specimens to study the effect of bulk continuous fibers (BCF) on the liquefaction resistance of low plasticity silt [17]. It can be seen from the above research results that fiber materials are widely used in sand, clay, expansive soil, and silt, which can improve the mechanical properties of the soil to some extent. Therefore, fiber can be added to iron tailings powder in order to improve the mechanical properties. Energy dissipation is a theoretical method which is often used to analyze the material failure characteristics, such as the calculation of slope safety factor, the constitutive relationship of geomaterials, the interfacial analysis of soil and structure, and the mechanical properties of soil and cement soil [18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28]. [PERSON] et al. explored the energy consumption of unreinforced and reinforced sand samples based on experimental and discrete element modeling (DEM) procedures [29]. On the basis of energy, [PERSON] and [PERSON] investigated the effect of fiber dosage, fiber length, confining pressure, and relative density on the cyclic shear resistance of fiber-reinforced sand [30]. Since energy is scalar, the shear energy dissipation of polypropylene-fiber-reinforced iron tailings powder can be regarded as the sum of the fiber interfacial energy dissipation and the direct shear energy dissipation of iron tailings powder. Shear performance is the most basic characteristic of geomaterials. Based on the energy dissipation theory, and referring to the research results of fiber-reinforced soil, the shear properties and interfacial strength parameters of fiber-reinforced iron tailings powder are studied.