Comparative study of Y-shaped and circular floating piles in consolidating clay

Abstract

Although engineers often make use of pile geometry to improve the axial load capacity of piles, geometrical effects on floating piles in consolidating clay are still not fully understood. This paper reports two centrifuge model tests to investigate the responses of a Y-shaped pile and a circular pile subjected to an induced dragload and applied axial loads. Three-dimensional numerical back-analyses were performed considering the elasto-plastic slip. The Y-shaped and circular piles developed similar downdrag but the dragload induced on the Y-shaped pile was larger than that induced on the circular pile. As the axial load increased, the neutral plane shifted upward along a nonlinear path which gradient of the Y-shaped pile was gentler. The ultimate bearing capacity of the Y-shaped pile was 1.73 times that of the circular pile. The dragload on the Y-shaped and circular piles was eventually eliminated at approximately 0.56 and 0.83 times the corresponding ultimate pile capacities, respectively. Three flanges of the Y-shaped pile "hung-up" adjacent soil which settled together with the pile shaft. The lateral extent of vertically non-uniform trapped soil decreased with increasing axial load. Even though the Y-shaped and circular piles encountered a similar serviceability limit state, Y-shaped pile had advantages in bearing capacity.

Discussion of “Comparative study of Y-shaped and circular floating piles in consolidating clay”

“…In the paper of Lv et al (2016), the effective stress method was used to calculate the ultimate shaft resistance (skin friction), f s , and was expressed as f s = ␤ v . This expression may be established based on the Coulomb's friction law, and can be written as…”

“…Following the suggestion of Lv et al (2016), eq. (4) was used to describe the relationship between the effective angle of shearing resistance of the surrounding soil, , and the friction angle of the pile-soil interface, ␦.…”

“…In the paper of Lv et al (2016), eq. (4) was used to describe the relationship between ␦ and , as shown in Fig.…”

“…In the numerical analyses of Lv et al (2016), the pile installation effect might not be considered in the program ABAQUS. The co- ͪ , and was computed as 0.188 when the value of of clay was adopted as 25°(see Table 3).…”

Discussion of “Comparative study of Y-shaped and circular floating piles in consolidating clay”

“…Based on the material parameters listed in Table 3 (Lv et al 2016) and the design methods for the analysis of the unit ultimate f s , e.g., eqs. (D1), (D2), and (D3), the unit limit f s of the model test pile embedded in the saturated clay can be determined, and can be summarized as follows.…”