Abstract: In field plate loading tests for the ground, the recommended size specified in the Technical Code for Testing of Building Foundation Soils (JGJ 340―2015), the commonly used size, and the actual size of the foundation often differ significantly, leading to discrepancies in determining the ground bearing capacity. A finite element model was established based on the results of the field tests to validate its reliability. Subsequently, the model was utilized to study the size effect on bearing capacity and deformation of both homogeneous and double-layered soil foundations under loading plates of varying widths. Furthermore, the impact of the reaction pier employed in the field test was analyze. The results indicate that with varying widths of the loading plate, the bearing capacity of homogeneous ground undergoes gradual changes, accompanied by noticeable settlement increments. The bearing capacity of double-layered ground, with a soft upper layer and a hard lower layer, increases with the width of the loading plate, resulting in reduced settlement. The presence of the reaction pier enhances the determination of bearing capacity. In the current testing code, the bearing capacity determined by ground relative deformation shows a significant size effect when the loading plate width is limited. It is recommended to adjust the upper limit of the loading plate width from 2.0 m to 3.0 m.

Key words: field plate loading test, size effect, numerical simulation, ground bearing capacity, width correction