Abstract：In order to study the bearing behavior of a single pile in sand under combined loads of vertical force V，horizontal force H and torque T，a special device for combined loads was designed and a series of model tests were carried out. The internal force-deformation under combined loads and the interaction curves of three loading components on the bearing capacity were obtained. The envelope of pile bearing capacity was obtained，and a simplified formula of the bearing capacity was given through dimensionless treatment and fitting. The results show that the effect of V and H leads to the reduction of torsional bearing capacity of the pile，for instance，the torsional bearing capacity is reduced by 66% under the combination of 0.6Vu-0.6Hu，compared with the ultimate torsional bearing capacity of pile shaft under pure T (Tu). Under combined loads，the pre-applied vertical load weakens the torsional bearing capacity of single pile，but improves the horizontal bearing capacity. However，the influence of H on the vertical bearing capacity can be neglected. There is a complex coupled relationship between the load components. The horizontal and vertical displacements of a pile increase with the increasing of T. The friction resistance and the horizontal reaction of piles interact，so the bearing capacity of composite pile cannot be evaluated simply based on the principle of superposition.
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2018, Vol. 37 
