土性经验公式在基桩极限承载力分析中的应用

Analysis of ultimate pile capacity based on empirical parameters of soil

针对粘性土和砂土的不同特性,分别给出了桩侧极限摩阻力及桩端阻力的工程经验公式。粘性土中桩侧极限摩阻力和桩侧阻力与土体的不排水抗剪强度联系在一起;砂土中桩侧极限摩阻力和桩端阻力与土体的上覆有效应力联系在一起,并考虑了大直径桩的应力释放效应。通过两个算例探讨了粘性土中桩无量纲极限承载力与桩身长细比、桩径及土体内摩擦角、不均匀系数的关系;探讨了砂土中桩无量纲极限承载力与桩体长细比、桩径和砂土极限状态摩擦角、相对密实度的关系。最后,通过一个工程实例对本文方法进行了验证。本文方法可在初步设计时预估基桩的承载力。

Considered the different features of sand and clay, empirical formulations for pile shaft resistance and pile base resistance are derived. Pile shaft resistance and pile base resistance in clay are related with the undrained strength of soil, while in sand they are related with the effective overburden stress. Meanwhile, the stress release effect of large diameter pile is also considered. For one of examples, the relation of non-dimensional ultimate pile capacity and pile slenderness, pile diameter, friction angle and coefficient of clay is analyzed. For another example, the relation of non-dimensional ultimate pile capacity and pile slenderness, pile diameter, critical state friction angel and relative density of sand is analyzed. Finally a project case is carried out to verify the method proposed in the text. The newly proposed method can provide a basis in the estimation of ultimate capacity of pile in the preliminary design.