In order to improve the bearing capacity, geotechnical engineers often take geosynthetic-encased measures at the top of the gravel pile. In order to analyze the influence on the ultimate bearing capacity of geosynthetic-encased gravel pile based on the column cavity expansion theorem conside the influence of the soil gravidity stress, the radius of the plastic zone and the bearing capacity calculation method were deduced when Mohr-Coulomb yield criterion was adopted. A new calculation formula based on the model, which considered the expansion overlapped between pile groups, was established. In order to validate the proposed method, a case history was illustrated. The result has indicated that these formulas are practical.