沉箱-钢管桩逆作法复合基础试验

为研究逆作法复合基础的荷载与沉降关系、桩土荷载分担特性以及钢管桩受力性能,进行了单桩、沉箱及沉箱-钢管桩逆作法复合基础系列模型试验.结果表明:采用沉箱-钢管桩逆作法复合基础,先施工沉箱及部分上部结构,而后续进行钢管桩的压、封桩能充分利用土体的承载能力,压桩前土体与沉箱底板保持严密接触,上部结构荷载全部由地基土承担;压桩后,土体得到了加固,沉降减小,承载力提高;封桩后,继续增加的荷载主要由桩体承担,直至桩达到极限承载能力;由于沉箱的影响,使桩身上部轴力衰减平缓,桩侧摩阻力被削弱,同时使桩身中下部轴力衰减加剧,侧摩阻力发挥得到增强;6倍桩距时,可不考虑群桩效应对逆作法复合基础的影响.

Experimental research on complex foundation of caisson-steel pile in top-down order

Model test s on the sing le pile, caisson and complex foundat io n o f the caisson-steel pile w ere designed to invest igate the relat ion betw een the bearing capacity and the set tlement , the load shear ratio betw een the soil and the pile, and the lo ad car rying proper ties of the steel pile. The result s indicate that the complex fo undat ion in top-dow n order w hich const ructes caisson and a par t of superst ructure first ly and then presses steel piles and seales the piles subsequent ly can take full adv antage of the soil bearing capacity , that the caisson plate kept in clo se contact w ith the foundation soil w hich bear al l of loads of the superst ructure befor e pressing piles, that the foundat io n so il is st reng thened af ter the pile pressed, the set tlement of the foundat io n decreases and the bearing capacity enhances, that most of the incremental loads are supported by the pile unt il the pile reaches the ult imate bearing capacity , that the inf luence o f the caisso n makes the dist ribut ion of the ax ial force gently and the frictio nal resistance decreases at the upper part of the pile, meanwhile fr ict ional r esistance at the rest part increases, and that the pile g roup ef fect can be neglected if the pile spacing is 6 t imes of the pile diameter.