The impact of gravity anchor deployment on the stability of gravel soil accumulation in bridges can be seen in the case of the Lugu Lake Super Large Bridge of Xixiang-Shangrila Expressway. The impact of gravity anchor reinforcement on the stability of the gravel soil accumulation body was examined. The deformation and failure characteristics of the gravel soil and the changes in its mechanical mechanisms were analyzed by establishing a triaxial test model under flexible boundary conditions through large-scale indoor triaxial tests and numerical simaulations using the particle flow code (PFC)-fast Lagrangian analysis of continua (FLAC) coupling technique. The results show that the initial elastic modulus E_i was positively correlated with the confining pressure in the triaxial tests. The cohesion decreased while the internal friction angle increases as the content of coarse particles in the gravel soil sample increased. Through fitting, a linear relationship between the failure strength σ_cre of the gravel soil sample in that area and the confining pressure σ₃ was obtained: σ_cre = 2.95σ₃ + 176.105. Under low confining pressure, the upper and lower conical regions of the triaxial sample continuously absorb energy, and two shear bands appear inside the gravel soil sample, forming an overall "X" shape. However, with the increase in confining pressure, the energy becomes redundant and spreads outside the shear bands, creating new cracks that mask the localized characteristics of the shear bands. As a result, the shear bands gradually decrease and disappear when the confining pressure reaches 400 kPa. The research results have certain reference value and guiding significance for the stability issues of gravel soil deposits.