软土中群桩承载变形特性与减沉复合疏桩基础设计计算

根据大型现场模型试验,分析了软土中群桩承台、桩、土相互作用特性。试验表明:随桩距增大,承台土抗力和桩侧阻力增大,而端阻力减小;当桩距增至6d时,侧阻力趋近于单桩,端阻力仍高于单桩,承台土抗力发挥率(承台效应系数)仅为50%左右,明显小于其他类土;桩基沉降变形特征表现为桩端刺入和桩间土压缩为主导;不同于小桩距群桩的桩、土整体变形特征。根据软土中疏桩基础承载变形特征,提出减沉复合疏桩基础简化设计方法,以计算桩间土压缩及桩土相互作用效应确定桩基沉降,并以十余项实际工程进行了验证。

Bearing capacity and deformation behaviour of pile groups in soft soil and design of composite foundation with settlement-reducing piles

Based on the field model tests on a pile group in soft soil,the cap-pile-soil interaction behaviour was analyzed.It was indicated that lateral friction of the pile group and soil reaction beneath the pile cap increased with the in crease of pile spacing,and the point resistance increased with the decrease of pile spacing the compared with single pile.When the pile spacing increased to 6d,the lateral friction of the pile group tended to equal to that of single pile,but the point resistance of pile group was still larger than that of single pile.The soil reaction beneath the pile cap increased with the increase of the pile spacing,and when the pile spacing increased to 6d,the soil reaction beneath the pile cap only developed 50% which was less than that of other kinds of soil.The settlement of the pile group with large pile spacing was mainly caused by pile punching and soil compression beneath the pile cap,obviously defferent form block deformation of pile groups with small pile spacing.Based on the above-mentioned characteristics of the pile group with large pile spacing,a simple design method for composite foundation with settlement-reducing piles was proposed to calculate compression of soil beneath the pile cap and pile-soil interaction in order to obtain the settlement of composite pile foundation.The proposed method had been verified with more than ten practical engineering projects.