多年冻土区管桩基础抗拔承载性能试验研究

以青藏直流联网工程为背景,进行上拔和水平力组合荷载作用下管桩基础抗拔承载性能真型载荷试验。结果表明:冻结期冻土地基整体处于冻结状态,地基回冻情况良好;融化期最大融化深度与地基多年冻土上限较吻合,多年冻土层无明显退化迹象。上拔加载过程桩底接触土压力减小,冻结期活动层范围内桩侧土压力明显增大,融化期活动层范围内桩侧土压力大大减小,其余位置土压力变化不明显。冻结期基础位移量显著低于融化期,冻结期抗拔及水平承载力高于融化期,上拔承载力高于水平承载力;上拔荷载与位移关系可采用幂函数模型进行预测。试验所得基础抗拔承载力与规范法计算结果比较吻合,表明冻土地区桩基础抗拔承载力规范计算方法是可靠的。

Experimental Research on Uplift Mechanism of Pipe Pile Foundation in Permafrost Area

Based on the Qinghai-Tibet DC Network Project, loading test was carried out to study the uplift bearing capacity of pipe pile foundation under vertical and horizontal loads. The experimental results show that the frozen soil foundation is wholly in the freezing state during the freezing period, indicating that foundation refreezing is in a good condition. During the thawing period, the maximum melting depth is corresponding with permafrost table and permafrost has no obvious sign of degradation. The pile end soil pressure decreases in uplift loading process. During the freezing period, side soil pressure of pile increases obviously in the permafrost active layer, while decreases significantly during the thawing period. The soil pressure of rest position has no obvious change. The displacement of pile is smaller in the freezing state than in the thawing state of active layer. The uplift and horizontal bearing capacity is higher in the freezing state than in the thawing state of active layer. Moreover, uplift bearing capacity is higher than the horizontal bearing capacity. The relationship between uplift load and displacement can be described by the power function model. The code calculating value of uplift bearing capacity is corresponding with the experimental result, signifying that the standard calculation method of uplift bearing capacity of pile in permafrost area is reliable.