## 1 Introduction
[11] verified the feasibility and high efficiency of the DDA method in the modeling of blasting. Using the DDA method, [PERSON] and [PERSON] [12] studied the influences of the blasting parameters, the joint characteristics of rocks, and the pressure on the blast-hole walls on the throwing process for blasted blocks. In terms of the simulation of the fracturing and fragmentation of rock masses, the mesh-free method, known as smoothed particle hydrodynamics (SPH), has also been widely used. [PERSON] et al. [13] took the lead in applying the SPH method to underwater blasting. Then, [PERSON] et al. [14] simulated blast waves and bubble motion by coupling the SPH method and the boundary element method (BEM). [PERSON] et al. [15] investigated the coupling of SPH and the finite element method (FEM) and evaluated the stability and efficiency of the model under different coupling parameters. Based on SPH-FEM coupling, [PERSON] et al. [16] explored the structural dynamic responses caused by underwater contact blasting. [PERSON] et al. [17] studied water inrush in the blasting excavation of tunnels based on SPH-FEM coupling. [PERSON] and [PERSON] [18] summarized new SPH-based algorithms and methods coupling SPH with other mesh or particle methods that have been developed for solving fluid-structure interaction (FSI) problems since the advent of SPH. The discrete element method (DEM) is also used to study the breakage and throwing of rocks in blasting. [PERSON] et al. [19] used PFC2D to simulate the relationship between the bench blasting parameters and the accumulated shape of blasted blocks. Based on the DEM, [PERSON] et al. [20] established a blasting model for limestone using FPC numerical software and applied the particle expansion loading algorithm to blasted particles to simulate the explosion process of explosives. [PERSON] et al. [21] built a 3D bench blasting model in which the rock strength follows the Weibull distribution using the discrete element software 3 DEC. Using the model, they simulated the dynamic breakage and throwing process for rocks in bench blasting with different initiating positions. [PERSON] et al. [22] proposed a bench blasting model based on 3 DEC by appropriately considering the size of blasted blocks and introduced the equivalent load, consisting of the pressure of stress waves and detonation gas, into the 3 DEC model. In recent years, the CFD-EDM method has been widely used to solve FSI problems in engineering, including for aerodynamic particle motion [23, 24], circulating fluidized beds [25], filter-cleaning devices for air conditioners [26], and solid-liquid mixed fluid in deep-sea mining pipelines [27]. Based on the coupling of Fluent and the Engineering Discrete Element Method (EDEM), [PERSON] et al. [28] simulated the pipeline plugging process and preliminarily studied the plugging mechanism for hydrates by considering the continuous fluid phases and discrete particle phases. Using Fluent-EDEM, [PERSON] et al. [29] introduced a dynamic mesh and found that the model could simultaneously analyze the flow fields and motion of small particles caused by the free movement of a large solid model. [PERSON] et al. [30] simulated the interaction between the seepage force and particles in a tunnel face using the CFD-DEM method. [PERSON] et al. [31] adopted the CFD-DEM coupling method to simulate the underwater casting process for concrete, concluding that the cement mortar at the top and margins is easily washed away by water. In summary, the block motion during underwater blasting involves a fluid-solid multi-phase coupling process. At present, application of DDA and SPH algorithms to underwater blasting still has some limitations [32]. To be specific, the DDA algorithm lacks an FSI module for fluid media and lumpiness, while the SPH algorithm, despite its ability to trace the material interface, has three shortcomings; namely, penetration of boundary particles, unstable tension, and structural anisotropy [33].