饱和黏土中不同刚度单桩水平循环加载离心试验

Centrifuge test on single pile with different rigidities in saturated clay under cyclic lateral loading

对正常固结黏土中具有不同桩土相对刚度单桩基础的水平静力及循环承载特性开展离心试验研究。在相同土层及桩基埋深条件下,通过调整模型桩材料及桩身截面几何尺寸,实现桩土相对刚度调节,对比组包括刚性桩、柔性桩和半刚性桩。在加载试验前执行T-bar循环插拔试验,各组试验土体强度与弱化参数一致,验证了制样的可靠性。桩基归一化荷载-位移曲线初始刚度和归一化极限承载力均随桩土相对刚度系数增大而增大,表明桩土相对刚度系数可用于描述水平受荷桩静力承载特性。尽管刚性桩刚度受循环荷载的影响更大,其循环稳定桩侧刚度仍显著优于柔性桩结果。循环稳定桩侧刚度与静力刚度比值随桩土相对刚度增大而减低,从长期刚度控制的角度,不断增大桩径不利于长期稳定承载,可通过增大桩基埋深提升长期承载的稳定性。

The centrifuge tests are carried out to investigate the static and cyclic lateral bearing behaviors of single pile with different pile-soil relative rigidities in normal consolidated clay.Under the same soil and pile-buried depth condition,the pile-soil relative rigidity is tuned by adjusting the model pile material and the section geometric parameter.The comparison group includes rigid pile,flexible pile and semi-rigid pile.Before the loading tests,the cyclic T-bar tests are performed,with the results indicating that the clay strength profile and softening parameter of each test are consistent,verifying the reliability of sample preparation.Both the initial stiffness and the ultimate bearing capacity of the normalized load-displacement curve of piles increase with the increase of pile-soil relative rigidity factor,which indicates that the pile-soil relative rigidity factor can be used to describe the static bearing behavior of the laterally loaded pile.Although the rigid pile is more affected under cyclic loading,its cyclic stable stiffness is still significantly larger than that of a flexible pile.The ratio of cyclic stable stiffness to static stiffness decreases under the increasing pile-soil relative rigidity factor.From the perspective of long-term stiffness control,increasing the pile diameter is not conducive to stable performance,which can be improved by increasing the pile-buried depth.