Evolution of the Soil Arching Effect in a Pile-Supported Embankment Considering the Influence of Particle Breakage

In pile-supported embankments, particle breakage commonly has a significant influence on soil properties, governing the load transfer induced by the soil arching effect. Thus, the influence of particle breakage on the soil arching effect in pile-supported embankments needs to be considered, especially through the operation period. Based on the three-dimensional discrete element method simulation on a pile-supported embankment model, the influence of particle breakage on the evolution of the soil arching effect is unraveled, including the initial, arching, static load, cyclic load, and after cyclic load states. The results indicate that particle breakage leads to a more significant degradation of the soil arching effect under the static load. Three stages for the evolution of the soil arching effect can be identified in the case of particle breakage under the cyclic load: the destruction of the original soil arching, the relaxation of the fragment, and the reformation of a new soil arching. These three stages are sequential due to the successive particle breakage above the pile and the primary and secondary independent particle breakage above the subsoil from a microscopic perspective. The new soil arching is less effective than the original one. In addition, the accumulative settlement on the embankment surface increases under cyclic load due to particle breakage, while the differential settlement on the embankment surface changes slightly.

In this study, the evolution of the soil arching effect in the pile-supported embankment was investigated through two cases with or without particle breakage. For a practical scenario, the particle breakage or the crushability index of the fill can be approximately evaluated based on the mineralogy of the soil particle. Under a given design load, the occurrence of the particle breakage can be assessed accordingly by an experimental method or numerical modeling. When particle breakage occurs, the soil arching effect is weakened, resulting in a decreasing load transferred to the pile cap. In other words, particle breakage is beneficial for the bearing capacity of piles. Nevertheless, when particle breakage occurs, the settlement on the fill surface increases, which is not favorable to the superstructures. In the engineering practice, these two issues should be jointly considered in pile-supported embankments with possible soil particle breakage, according to the requirement and desire of the design.