缩径承台基桩竖向承载力及桩周土体变形

Vertical Bearing Capacity and Soil Deformation of Necking Piles With Pile Cap

为了探究含缩径缺陷的承台基桩竖向承载性能和桩周土体变形规律,以缩径位于桩体深部为例,对1根完整承台基桩和6根缩径承台基桩进行了室内透明土模型加载试验,得到了桩荷载-沉降曲线。通过数据处理,得到承台沉降4 mm(极限承载力)时的桩周土体位移场。研究了缩径轴向尺寸和径向尺寸对承载力和桩周土体变形的影响规律,给出了承载力的变化原因。研究结果表明:缩径会严重影响基桩承载力,当轴向尺寸为20 mm、径向尺寸为8 mm时,极限承载力损失可达17.59%。承台和缩径周围的土体产生了较大的变形,减少了桩与土之间的相对位移。随着缩径轴向尺寸和径向尺寸增大,土体变形增大。缩径周围和桩端之间的土体发生贯通现象,桩与土体产生了同步位移,且随着缩径尺寸越大,贯通现象越明显。承台和缩径周围的土体与桩之间的相对位移,以及缩径周围与桩端之间的土体产生的贯通现象导致桩的侧摩阻力降低,从而损失了桩的承载力。

To investigate the impacts of necking on the bearing capacity and soil deformation of single pile cap,this paper took the necking located in the deep pile shaft as example.Based on transparent soil model experiment,one intact pile and six necking piles were loaded to get the load-settlement curves.Through data processing,the displacement field of soil around pile was obtained when the settlement of pile cap was 4 mm(ultimate bearing capacity).The influences of necking axial size and radial size on the bearing capacity and soil deformation around piles were studied,and the reasons causing the bearing capacity to lose were explained.The research shows that the necking will seriously affect the bearing capacity of foundation pile.When the axial dimension is 20 mm and the radial dimension is 8 mm,the loss of ultimate bearing capacity can reach 17.59%.The soil around the pile cap and the reduced diameter produces large deformation,which reduced the relative displacement between the pile and soil.With the axial and radial dimensions of the necking increasing,the soil develops larger deformation.The soil around the necking and between the pile end has a penetration phenomenon,and the pile and soil have a synchronous displacement.The larger the reduced diameter is,the more obvious the penetration phenomenon is.The relative displacement between the pile and the soil of pile cap and necking,as well as the penetration of the soil around the necking and between the pile end,leads to the reduction of the side friction of the pile,thus losing the bearing capacity of the pile.