Abstract: Physical model test is an effective means to study the deformation and fracture characteristics, dynamic process, and genetic mechanism of geological disasters. Limited by the size of model box, the boundary effect is significant in the test process, so how to reduce the influence of boundary effect has always been the focus of researchers. In this study, the physical model test of the rupture propagation of buried ground fissures was taken as the research object， and the boundary effect of physical model box was systematically analyzed by means of phenomenal analysis of the physical model tests and numerical simulation verification. The results show that the main controlling factor of the boundary effect of the model box is the ratio of sidewall damping to box size. The sidewall damping is positively correlated with the amplitude of the boundary effect. When the sidewall friction angle is smaller than the internal friction angle of the soil, the cohesion is the main factor affecting the boundary effect. When the friction angle of the sidewall is larger than the friction angle of the soil, the friction is the main factor affecting the boundary effect. The box size ratio affects the amplitude of boundary effect, and the aspect ratio is positively correlated with the amplitude of boundary effect. The box boundary effect has a significant influence on the results of the physical model test on the fracture propagation of buried ground fissures. The optimal size ratio of the experimental model box is determined to be 5∶3∶2.2.

Key words: buried ground fissure, rupture propagation, physical model tests, numerical simulation, boundary effect