## 1 Introduction
[11] studied the erosion wear on pipelines caused by high-concentration fly ash slurries using a modified pot tester and found that erosion has a stronger dependence on concentration than on relative velocity. [PERSON] and [PERSON] [12] presented a model predicting pipeline erosion from smooth river sands, and particles with diameters of 50 to 350 \(\upmu\)m, velocities of 3.5-6 m/s, and sand slurry concentrations of 10-40% by volume were considered in the model. [PERSON] et al. [13] presented a review of the literature covering research into the effects of the main parameters influencing the slurry erosion of different types of steels and discussed the types of bench-scale erosion test rigs, the mechanisms involved, and the behaviors of different microstructures under slurry erosion conditions. With the continuous development of computer technology, computational fluid dynamics combined with discrete particle models (CFD-DPM) have been introduced into the study of pipe wear. [PERSON] et al. [14] investigated the erosion wear of a 90\({}^{\circ}\) elbow pipe using the computational fluid dynamics code FLUENT and found that the erosion wear increased exponentially with velocity, particle size, and concentration. [PERSON] and [PERSON] [15] developed a web-based erosion-corrosion model for dense, settling, horizontal, aqueous slurry pipe flow in oil sands and mining applications and explored the validation of the model. [PERSON] [16] presented an overview of the particulate wear that occurs in various components of slurry pumps, pipeline systems, and hydraulic turbines due to the mechanical action caused by the flow of solid-liquid mixtures and discussed further investigations to develop more accurate and flexible models that can be used to predict the particulate wear in a wide range of applications. Different from the abovementioned industrial applications, the slurry transport of rock particles during slurry shield driving has two evident characteristics. The first concerns the size of the particles that should be carried. Natural particles (sand, pebble, gravel,cobble, etc.) accrue in slurry discharge pipelines when tunneling in pebble and cobble ground, and rock fragments from rock cutting accrue when tunneling in rock ground or rock-soil interface mixed ground. The maximum particle sizes encountered possibly lie between several centimeters and more than tens of centimeters in large-diameter slurry shield tunneling. The sizes of the involved particles in other industrial applications are small and usually range from tens of microns to several millimeters. The second characteristic is the carrier used. When slurry shield tunneling in difficult ground, such as pebble and cobble layers, the liquid carrier fluid must form a filter cake at the cutting face to guarantee the initial safety of the cutting face. Usually, specially prepared suspensions composed of bentonite, carboxymethyl cellulose, water, and other additives are employed as the support medium, which also act as carriers to convey excavated rock particles. These suspensions have a higher density and viscosity, and their physical and mechanical properties are much different from the carriers of water or gas used in other industrial applications. These two characteristics together contribute to the different action mechanisms between rock particles and pipelines, severely damaging and wearing down the slurry discharge pipelines of a slurry shield machine. However, the literature on rock-particle-induced damage and wear of slurry discharge pipelines is limited. A typical example was centered on pipe wear caused by Bukit Timah granite rock fragments in Singapore.