This paper presents the study of negative skin friction of the superlong pile caused by the soil settlement under large-scale surcharge loading. Based on the displacement equilibrium principle and transfer matrix method, with the introduction of a load transfer model considering shaft resistance softening, the analytical model of negative skin friction of superlong pile under surcharge loading is established by considering the three-dimensional consolidation settlement along the pile under surcharge loading, the compression deformation of pile, and the soil settlement around pile-end. Three-dimensional Biot consolidation is used to derive the settlement of soil surrounding pile and the settlement formula is simplified by using the Laplace and Hankel integral transform. Furthermore, the analysis is conducted for an engineering example using the theoretical model and FEM simulation method. The results are also compared with the corresponding measured data. The characteristics of negative skin friction of superlong pile under surcharge loading are obtained, and the effect of soil parameters on negative skin friction is discussed as well, which can offer valuable reference for the design of superlong piles.

The current researches on soil-pile interaction under combined action of axial and lateral loads are mainly focused on the short or middle-long piles in a homogeneous soil. The practice for design of piles subjected to both axial and lateral loads commonly considers the two loads separately. In this paper, a super-long pile group in stratified soils under both vertical and lateral loads and the pile-soil interaction with the pile cap in contact with ground are all simulated together by a three-dimensional nonlinear numerical model. The influence of lateral loading on the vertical pile stresses and bending moments is analyzed. In addition, the effect of vertical loading on the lateral pile response is also investigated. On the other hand, given the fact that the super-long pile group is relatively insufficient in resisting a large lateral load, the pile in shallow depth is sleeved to reduce the horizontal displacement. Using the sleeve, the lateral load is transferred onto the deeper soil mass. The results show that the sleeved super-long pile group proposed in this paper can reduce the horizontal displacement significantly and is feasible in practical applications.

In this study, we investigate the coupling of an internal field (defect field-sp³ bonds and nanopores) and an external field (strain and temperature).

One of the miraculous functions of graphene is to use its defects to alter the material properties of graphene composites and, thereby, expand the application of graphene in other fields. In this paper, various defects have been created in graphene by using ion irradiation. Defective graphene is sandwiched between two copper layers. A numerical model of Graphene/Copper layered composites after irradiation damage was established by the molecular dynamics method. The effects of ion irradiation and temperature coupling on defective graphene/copper composites were studied. The results show that there are a lot of empty defects in graphene after irradiation injury, which will produce more incomplete bonding. Although the bonds between carbon atoms can be weakened, defective graphene still enhances the mechanical properties of pure copper. At the same time, the location and arrangement of defects have a great influence on the mechanical stability of graphene/copper composites, and the arrangement of empty defects has different effects on deformation behavior and the stress transfer mechanism. It can be concluded that the defects formed by radiation have an effect on the physical properties of two-dimensional materials. Therefore, irradiation technology can be used to artificially control the formation of defects, and then make appropriate adjustments to their properties. This can not only optimize the radiation resistance and mechanical properties of nuclear materials, but also expand the application of graphene in electronic devices and other fields.