局部倾斜桩竖向承载力的有限元研究

桩基会由于隧道或基坑开挖、打桩顺序不当等原因而倾斜。实际工程中经常遇到桩局部倾斜的情况，例如上段桩发生弯曲与倾斜，下段桩则仍然保持竖直。在已经完成的整体倾斜桩现场试验及有限元分析基础上，建立了桩身局部倾斜的有限元模型，对局部倾斜桩的承载力进行有限元分析。分析结果表明：算例条件下相同竖向荷载作用时，垂直度在5 %以内的局部倾斜桩的桩顶沉降均小于竖直桩的桩顶沉降；垂直度超过5 %时局部倾斜桩的桩顶沉降大于竖直桩的桩顶沉降。相同竖向荷载作用下垂直度为7 %以内局部倾斜桩的桩顶沉降均小于相同垂直度整体倾斜桩的桩顶沉降，超过7 %后局部倾斜桩的桩顶沉降大于整体倾斜桩的桩顶沉降。对于局部倾斜桩，由上段倾斜桩传递到垂直度转折点处的轴力将对下段竖直桩产生水平向推力。当垂直度转折点深度在反弯点以下时，水平向推力将导致下段竖直桩产生更大的反向挠曲变形和弯矩，使竖向荷载作用下桩顶水平位移增加，使桩更易于因为水平弯曲变形过大而破坏。

Research on vertical bearing capacity of partially inclined pile with finite element method

Pile may incline due to the excavation of tunnel or pit, incorrect driven sequence and other reasons. It is a common practice that pile inclines partially. For example, the upper part of a pile inclines due to flexural deformation while the lower part still remains vertical. Based on the results from load-tests on totally inclined piles and finite element analyses, finite element models are constructed to analyze the bearing capacity of partially inclined pile. Finite element analyses show that under the same vertical load, settlement of partially inclined pile with the degree of inclination within 5 % is smaller than that of vertical pile. When it is above 5 %, settlement of partially inclined pile is greater than that of vertical pile. Under the same vertical load, settlement of partially inclined pile with the degree of inclination within 7 % is smaller than that of totally inclined pile with the same degree of inclination, while when it is above 7 %, the trend reverses. For partially inclined pile, axial load transferred to the top of lower part of inclined pile will produce a lateral force on the lower part, which will lead to larger inflection deformation and moment in the lower part of the partially inclined pile especially when the joining point is below the point of inflection. The deeper the joining point, is the greater the lateral displacement is at partially inclined pile top, which will certainly make it easier for the inclined pile to fail due to excessive flexural deformation.