粉质黏土中沉箱—桩复合基础水平向承载性能试验研究

Experimental study of horizontal bearing capacity of caisson-pile composite foundation in silty clay

为进一步研究沉箱-桩复合基础的水平向承载性能,开展粉质黏土中单桩、沉箱-桩复合基础在水平向荷载和竖向及水平向组合荷载作用下的系列试验,对沉箱-桩复合基础的水平荷载与位移关系、桩身弯矩、位移及土抗力分布规律及群桩效应等进行了研究。结果表明,在水平荷载作用下沉箱对桩顶的约束使桩身弯矩分布较桩顶自由情况要更均匀,并能有效地降低桩身弯矩、位移及土抗力,提高了基础水平承载能力;在同时作用有竖向和水平向组合荷载时,沉箱底摩擦力参与抵抗水平力作用、桩顶竖向力也有利于进一步提高基础水平承载力;试验获得了不同桩数、桩顶约束、荷载作用条件下的沉箱-桩复合基础群桩效应系数,对于桩距为6倍桩径的情况,桩与桩之间的相互影响很小。

To make further research on the horizontal bearing capacity of caisson-pile composite foundation, the model tests on single pile and a series of caisson-pile composite foundations, under horizontal loads and the combination of vertical and horizontal loads in silty clay, are carried out. The relation between load and displacement, bending moments of pile shaft, lateral deflections of pile shaft and efficiency coefficients of group piles are investigated based on the model tests. With the constraint of caisson, the bending moments, displacements and soil resistance of pile shaft under the horizontal loads, can be reduced than the single pile without constraint; the horizontal bearing capacity of composite foundation can be improved. Under the vertical and horizontal combination loads, friction under the caisson bottom and vertical force on the pile top is also conducive to further improve the composite foundation bearing capacity. The efficiency coefficients of caisson-pile composite foundations with different pile numbers, constraint conditions on the pile top and loads on caisson are also obtained. For the case of pile distance is 6 times of the diameter, the mutual influence between each other pile is very small.