深厚软土区超长群桩有效桩长确定方法

Determination Method of Effective Length of Super Long Pile Group in Deep Soft Soil Area

将单桩有效桩长概念延伸至深厚软土区超长群桩基础中以确定其有效桩长。首先,引入剪切位移法推导得出群桩中各基桩桩侧摩阻力在桩周土中产生的位移场,并考虑因各桩的存在所引起的位移折减效应,建立了基于桩-桩相互作用的桩侧单位厚度土等效刚度系数表达式。在此基础上,基于荷载传递法建立了各基桩的荷载传递微分方程,并考虑超长桩的荷载传递特性,建立了群桩有效桩长与桩顶容许沉降量之间的关系式,从而得出基于沉降控制的深厚软土区超长群桩有效桩长计算方法,并通过算例验证了该方法的可行性。最后,基于该方法对影响深厚软土区超长群桩有效桩长的各主要设计参数进行了对比分析。结果表明:桩顶荷载、桩土相对刚度及桩径对群桩有效桩长的取值较为敏感,其中,群桩有效桩长随桩顶荷载、桩土相对刚度的增大而呈非线性增长,但随桩径的增大而减小;桩间距对群桩有效桩长的影响相对较小。

The concept of single pile effective length was extended to the super long pile group effective length in the deep soft soil area to determine its effective length. Firstly, sheardisplacement method was introduced to obtain the friction of each single pile and its displacement in the soil, then considering displacement reduction effect due to the other piles, the model forthe expression of the unit thickness soil equivalent stiffness coefficient based on pile-pile interaction was established. Based on the load transfer method, the load transfer differentialequation of each pile was established and considering the super long pile load transmission, the relation between the pile group effective length and the pile allowable settlement was established,so the determination of effective length of pile group in the deep soft soil area was obtained. At last, based on the method of this paper, the main parameters of super long pile group effectivelength in the deep soft soil area were compared. The results show that the pile load, pile-subsoil stiffness and pile diameter are sensitive to pile group effective length, in which pile groupeffective length increases nonlinearly with the increasing of the pile load and pile-subsoil stiffness but decreases with the increasing of the pile diameter, and pile spacing has a relatively minorinfluence on the pile group effective length.