On Bearing Behavior Of Single Pile Under Combined Horizontal And Uplift Loading

Facing the increasingly complex external environment,the forces on the pile foundations will become more complex.Piles used for underground building(structures),high-rise structures and transmission towers are often subjected to combined horizontal and uplift loading.In practice,horizontal and pullout loading is considered to act on the pile top separately,and the horizontal and uplift bearing capacity and deformation of the pile foundation are calculated,which without considering the effect of the coupling effect.At present,how does the uplift(horizontal)load affect the horizontal(uplift)bearing capacity and deformation of single pile is still no consensus on the impact.Compared with the pile-soil system under horizontal or uplift load,will the combined loading affect the interaction? What impact will it have? And the bearing mechanism of pile foundation under combined loading? These problems still need to be answered,so following researches was implement.Based on the self-made combined loading device,the horizontal loading model test was carried out on the single pile under the influence of different uplift loads.The test results show that applying the uplift load first is beneficial to the horizontal load of the single pile;increasing the uplift load reduces the maximum bending moment under the same horizontal load and weakens the horizontal stiffness of the foundation.The horizontal bearing capacity of the combined load pile is analyzed from the P-? effect,friction effect and soil unloading effect.The results show that the effect of the uplift load on the horizontal bearing capacity of a single pile and the pile diameter and the roughness of the pile body related.A numerical simulation study on horizontal loading of engineering piles under the influence of uplift load was carried out.The research results show that the uplift load applied first has little effect on the horizontal ultimate bearing capacity of the engineering pile;increasing the uplift load can reduce the maximum bending moment value of the pile body under the same horizontal load,and the pile displacement and pile shear Force basically has no effect.Further parameter analysis shows that the pile length and lateral pressure coefficient have basically no effect on the above law;when the pile diameter becomes 0.4m,the uplift load has a small lifting effect on the ultimate horizontal bearing capacity of a single pile.A model test of uplift loading of a single pile under different levels of load was carried out.The test results show that the ultimate uplift bearing capacity of a single pile increases with the increase of the pre-applied horizontal load;the horizontal load applied first mainly increases the friction resistance in the range of 0-10 D,and the friction resistance of the following pile body no effect.Combined with the existing research results,a prediction formula for the ultimate pull-up bearing capacity of the combined load pile is given,and its calculation error is within 6%.Based on the numerical model,the numerical simulation analysis of the uplift bearing behavior of the engineering pile under the influence of horizontal load is carried out.The analysis results show that the ultimate pull-up bearing capacity increases with the increase of the horizontal load applied first,and the increase rate is related to the pile diameter,pile length and lateral pressure coefficient.