锥台型装配式基础冻拔与抗压承载性能模型试验

Model tests on frost jacking behavior and compressive bearing capacity of cone-frustums assembly foundation

针对冻土地区输电线路工程杆塔基础的冻拔破坏问题,提出了一种锥台型装配式基础。通过大型冻土模型试验,考察该基础在不同冻结环境条件下的冻拔特性和抗压承载性能。试验结果表明:(1)基础的冻拔位移低于周围地表冻胀位移,地基冻胀量随着与基础距离的增大而增大,该种基础具有良好的抗冻拔性能,且对地基冻胀变形具有限制作用;(2)在冻土地基条件下,基础的下压荷载-位移曲线呈现"缓变型",随着冻结环境温度的降低,曲线位置逐渐向右侧移动,基础的抗压承载性能逐渐增强;(3)基础的极限抗压承载力随着冻结环境温度呈线性增长规律,变化速率约为10.5 kN/℃,基础的破坏是由温度应力与外加荷载共同作用所引起的,外荷载的作用导致地表前期产生的冻胀裂缝进一步拓宽、延伸,最终导致地基基础体系发生破坏。

In view of the failure of transmission line tower foundation in frozen soil area,a new type of cone-frustums assembly foundation was proposed.Based on the large-scale frozen soil model test,the frost jacking behavior and compressive bearing capacity of the foundation under different frozen environment conditions were investigated.The results showed that:(1) the frost uplift displacement of the foundation was lower than the frost heave displacement of the surrounding surface,and the frost heave displacement of the soil around the foundation increased gradually with the increasing of the distance from the foundation.This kind of foundation had good frost uplift resistance and had a limiting effect on the frost heave deformation of the foundation.(2) Under the condition of frozen soil foundation,the load displacement curve of test foundation presented "gentle slope".With the decreasing of freezing environment temperature,the curve position moved to the right gradually,and the bearing capacity of test foundation increased gradually.(3) The ultimate bearing capacity of test foundation increased linearly with the freezing environment temperature,and the change rate was about 10.5 kN/℃.The damage of foundation was caused by the combined action of temperature stress and external load.The effect of external load leads to extension of frost heave cracks in the early stage of the surface,which eventually leads to the damage of foundation system.