At present, the simulation of dam break flood mostly adopts the segmented method of calculating the evolution of the breach and the flood propagation process, respectively; that is, firstly, the development process of the breach is calculated by using the parameter model or the mechanism model to obtain the flow process of the breach, and then the result is used as the input of the flood evolution model. However, the process of dam break is a process involving the hydraulic power of the upstream reservoir area, the evolution of the breach, and the flood propagation in the downstream simulation area. The reduction in reservoir water level, the development of the breach, and the flood propagation process in the downstream area are carried out simultaneously, and they affect each other. The level of local water level before the breach directly affects the development of the breach, the development of the breach determines the discharge volume, and the breach discharge determines the difference of the downstream inundation situation. The dam break process is more consistent with the real process by solving the dam break process and downstream flood propagation in the same time step. Based on this, [PERSON] [33] established a mathematical model, which adopted a one-dimensional model in the upstream reservoir area, a two-dimensional hydrodynamic model in the downstream inundation area, and adopt weir formula to connect the dam breach. However, in this model, the breach process was relatively simple, and the soil dynamics of the evolution of the collapse were not considered. [PERSON] [34] used the source term method to establish a coupling model which included the two-dimensional hydrodynamic process of the upstream reservoir, the one-dimensional evolution of the breach, and the two-dimensional propagation of the flood in the downstream simulation area, but the traditional weir flow formula was used to calculate the flow of the breach. At the same time, the two-dimensional propagation of dam break flood generally has a long distance, a large range, and a high dependence on terrain. The high-precision terrain can make the simulation results more accurate but will lead to an increase in calculation. [PERSON] [35] developed a two-dimensional hydrodynamic model, IBER, which coupled the evolution of a breach and the propagation of a flood. IBER can be calculated by CPU or GPU with high performance. However, the breach evolution module includes two types, one can be defined by users, and the other follows the specifications of the Spanish Technical Guide [36] of the parameter model, and the physical mechanism is poor. [PERSON] et al. realized large-scale flood evolution simulation through the cluster computing technology based on message passing interface (MPI) [37]. [PERSON] developed a two-dimensional hydrodynamic model based on GPU parallel acceleration technology [38]. Parallel computing and the use of HPC on new architectures of modern supercomputers have become fundamental requirements for studying hydrodynamic problems at large spatial scales and high temporal resolution. However, in the high-performance hydrodynamic models of these coupled dam break models, the calculation of the outflow is mostly based on the weir flow formula, or the physical mechanism of the breach development is not fully considered. Therefore, although physics-based breach development models developed rapidly, it is still necessary to improve the models, and to better match the real breach process, it is necessary to solve the dam failure process and downstream flood evolution in the same time step. This paper incorporates the seepage impact based on stress analysis of soil particles, and a novel horizontal expansion mechanism is proposed. Simultaneously, the dam break model is integrated with the two-dimensional hydrodynamic model utilizing multi-GPU acceleration technology.