The Pile End Mechanism of Jacked Pile in Layered Soils

The research on penetration mechanism of jacked pile has been the focus of pile engineering. However, the majority of literature was limited in scope to homogeneous foundation and the layered effect was commonly ignored. With this consideration, the aim of this paper is to investigate the layered effects on pile end resistance for jacked pile penetration. For this purpose, an indoor model test is conducted to simulate the pile penetration process. In this test, the variation law of the pile end resistance with the penetration depth in different layered soil during the jacking process is revealed and the influence zone of various soil layers on pile end resistance is discussed in detail. Based on the model test, the discrete element numerical simulation of pile driving process is performed in layered soils and results are compared with experimental data. Results from this study show that the zone of influence in different soil layers can be influenced by soil properties, such as strength and stiffness. When the pile end is outside the influence zone of soil layers, the pile end resistance infinitely approaches that of homogeneous foundation at the same depth. Besides, there are approximate linear relations between the ratio of zone of influence in soil layer to pile diameter ( $$Z_{{\text{s}}} /D$$ , $$Z_{{\text{w}}} /D$$ ) and the minimum value of pile end resistance ratio ( $$\eta_{\min }$$ ). Numerical simulation results are well consistent with the model test results. The research results are helpful to estimate the variation law of pile end resistance in layered foundation and have guide significance for the design and construction in jacked pile engineering.