# Grouting Process Simulation Based on 3D Fracture Network Considering Fluid-Structure Interaction
## 1 Introduction  
Many high dams are built in areas with complicated geological conditions, and the numerous fractures and voids will increase the permeability and decrease the strength of the rock mass, which affect the stability and safety of the dam's foundations. As a common and effective measure to improve the geological conditions of dam foundations, grouting is used to fill up the joints and fractures in the rock mass so as to prevent seepage and improve the bearing capacity and deformation resistance [1; 2; 3; 4]. However, fracture grouting is still a difficult issue due to complicated fracture distribution, complex fluid-structure interaction effects, and incomplete information on grout diffusion behavior and corresponding fracture deformation. In order to reveal the grouting mechanisms in the fractured rock mass, it is necessary to select an effective tool for studying the grouting process, especially for considering the fluid-structure interaction. Computational fluid dynamics (CFD) is an effective tool used to simulate fracture grouting, which can partly overcome some limitations of experiments. In recent years, various researchers have carried out an abundance of research. [PERSON] et al. [PERSON] et al. (2018) established a numerical model to study the effect of fracture properties on grout flow and penetration length in fractured rock mass using Universal Distinct Element Code (UDEC). [PERSON] et al. [PERSON] et al. (2018) simulated the cement grout diffusion process in a single rough fracture by the finite element method. [PERSON] et al. [PERSON] et al. (2018) performed numerical simulation on the diffusion process of cement grouting in the fractures of the rock mass to determine reasonable hole spacing and other parameters. [PERSON] et al. [PERSON] et al. (2018) developed a numerical simulation of polymer grout diffusion in a single fracture to analyze the pressure distribution. [PERSON] et al. [PERSON] et al. (2018) proposed a CFD simulation approach based on 3D fracture network model to study the grouting process of a dam's foundation. [PERSON] et al. (2018) used UDEC to simulate the flow of Bingham grout in a single joint with smooth parallel surfaces and considered the hydromechanical coupling to study its effect on grouting performance. [PERSON] et al. [PERSON] et al. (2018) simulated the grouting process in underground goaf and analyzed the stability by applying one-way fluid-structure interaction. [PERSON] et al. [PERSON] et al. (2018) combined a finite-discrete element method (FDEM) and a grouting flow simulator to consider the hydromechanical coupling effect in the parallel-plate model. The review of previous studies reveals that most of the aforementioned approaches simulated the grouting process in a single fracture, 2D fracture network or simplified rock mass, which cannot reflect the actual diffusion of grout flow in complex fractured rock mass completely. Furthermore, these studies only studied the diffusion of grout in fractures or the effect of grout on the rock mass, without taking the complex fluid-structure interaction between grout flow and rock mass into account, which were different from the actual conditions. In order to obtain a more realistic simulation of grouting process, the establishment of a precise and reliable three-dimensional fracture network model is an important prerequisite [PERSON] et al. (2018). Since deterministic data of the fracture aperture are not available, in current studies of fracture network modeling and its application the fracture aperture is usually ignored [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018), reduced to a given value [PERSON] et al. (2018), or randomly generated from a given range or geologically conditioned statistical distributions [PERSON] et al. (2018); [PERSON] et al. (2018). The fracture aperture significant influence the permeability of the fractured rock masses, so it is necessary to establish a fracture network model with a more authentic and accurate fracture aperture to simulate the grouting process.