# Grouting Process Simulation Based on 3D Fracture Network Considering Fluid-Structure Interaction
## 1 Introduction
For fractured rock mass, fractures are usually random and complex which are fractal structure with self-similarity; according to this characteristic of a fracture, some scholars have put forward the formula for the relationship between fracture apertures and trace lengths, and this relationship has been widely investigated [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018). In this study, this relationship will be introduced into the fracture network modeling to make up for the deficiency of the existing research. As the pressurized grout penetrates the fractures inside the rock mass, the grout will separate the fracture surfaces from each other, causing an interaction between the grout and the rock mass [PERSON] et al. (2018). [PERSON] et al. [PERSON] et al. (2018) indicated the coupling of processes implies that the both interact in the initiation and progress of each other. On the one hand, the grout pressure induces stresses on the surfaces of the fracture, this will lead to the deformation of the fractures. On the other hand, the change of the fracture aperture will affect the fracture permeability, and then results in the variation of grout performance. So the grouting performance cannot be determined by considering each process independently. Some theoretical studies on the interaction between grout and rock mass have been carried out. [PERSON] and [PERSON] [PERSON] and [PERSON] (2018) analyzed the interaction of two parallel fracture during high pressure grouting and discussed the effect of fracture dilation on the penetrability of fine fractures. [PERSON] and [PERSON] [PERSON] and [PERSON] (2018) proposed a procedure for optimizing grouting pressure based on the estimation of grout spread and the identification of jacking of the fracture. [PERSON] and [PERSON] [PERSON] and [PERSON] (2018) described the basic mechanism of elastic deformation during grouting and discussed its impact on the spread of grout. In literature [PERSON] et al. (2018), the authors strongly recommended that the interaction between the grout flow and fractured rock mass should be included in the grouting analysis in order to have a precise prediction of grout performance. With this in mind, the fluid-structure interaction (FSI) method as a numerical technique is used to solve problems that involve the mutual interaction of fluid and structure. Inrecent years, with the development of computer performance and increasing interest in more realistic modeling, FSI has attracted extensive attention in the computational field [25]. For instance, this technique has been applied in the problem of internal slip during the operation of progressive cavity pump (PCP)s in oilfield production [26], biomedical problems where blood flow interacts with blood vessel walls [27], and the fluid-structure interaction problem of fracturing structures under impulsive loads [28]. Of interest from a fractured grouting perspective, there is still much work to do in the grouting simulation considering fluid-structure interaction to capture the interaction between grout flow characteristics and deformation of the fractures. In summary, most of the existing studies simulated the grouting process in a single fracture, 2D fracture network or simplified rock mass, which is inconsistent with actual fractures under complex geological conditions. Moreover, the value of fracture aperture is usually ignored or inaccurate in the fracture network modeling, which will affect the authenticity of grouting simulation. Additionally, rich theoretical research achievements have proposed on the interaction between grout and fracture, and some of the grouting simulations considering fluid-structure interaction are based on single-fracture or just using one-way fluid-solid coupling. Therefore, based on the 3D fractured network model the numerical simulation of the grouting process considering two-way fluid-structure interaction still needs further study.