水泥土桩复合地基荷载传递及变形的原位试验研究

为了获得桩长、置换率等对水泥土桩复合地基荷载传递及变形的定量影响,在5组4桩群桩和5组9桩群桩复合地基的桩体内埋设应变计,在桩间土体内埋设深层沉降标,实测到4桩群桩和9桩群桩复合地基中桩体轴力分布、桩侧摩阻力分布和桩间土变形分布。发现置换率相同时,承台板宽度大,水泥土桩的荷载临界深度也大,桩侧摩阻力分布深度下移。承台板宽从1.0m增加到1.5m时,荷载临界深度由14倍桩长增加到18倍桩长。变形影响深度约为承台板宽度的(1.8～2.5)倍。最大摩阻力出现在承台下1.5m处,该处的竖向偏应力最大,桩体容易在这里破坏。增加桩长能有效减少沉降。荷载水平达到70%以后,变形影响深度下移不再明显。

Field test on the load transfer and deformation of cement-soil pile group

To obtain the quantitative influence of pile length and replacement ratio on the load transfer and displacement of cement-soil pile groups,strain gauges were mounted on the cement-soil piles and deep settlement instruments buried in the soil,for a total of five 4-pile groups and five 9-pile groups.The axial force along the pile shaft,the skin friction and the soil settlement were measured.It is found that the load critical depth and the friction range increase while the cap breadth increases with the same replacement ratio.The load critical depth changes from 14 to 18 times of the pile diameter while the cap breadth varies from 1.0m to 1.5m.The deformation influence depth is about 1.8 to 2.5 times the cap breadth.The maximum friction occurs at about 6 times of the pile diameter(1.5 m)beneath the cap.Long pile can significantly reduce the settlement.However,the deformation influence depth does not increase when the load-level is equal to or exceeds 70%.