砂土中竖向和水平荷载共同作用下的单桩承载特性研究

水平荷载引起桩体水平位移,导致桩侧摩阻力发生变化,从而影响单桩的竖向承载特性;竖向荷载影响桩周土体抗力,并随着桩身挠曲变形而产生附加弯矩,从而影响单桩的水平承载特性。利用室内模型试验研究了砂土中单桩在竖向和水平荷载共同作用下的受力和变形特性。试验结果表明:预先施加竖向荷载有利于单桩水平承载力的提高和水平位移的减小;预先施加水平荷载对桩身上部桩侧阻力的发挥有减小作用,但水平荷载的增大对桩端阻力的发挥有促进作用,总体上表现为预先施加水平荷载削弱了单桩的竖向承载力;单桩水平荷载引起的最大弯矩位置在地面以下约5d~7d处,水平荷载对桩身弯矩和桩侧摩阻力的影响主要集中在地面以下0~10d的深度范围内。结合已有研究成果和理论分析,验证了试验成果的合理性并从理论上分析了砂土中竖向和水平荷载共同作用下的单桩承载机理。

Study on bearing behavior of a single pile under combined vertical and lateral loads in sand

The vertical bearing behavior of a single pile is influenced by change of the friction resistance of soils around the pile, which is caused by the lateral deformation of the pile. Around the pile, the lateral resistance of soils can be affected by vertical load, and meanwhile with the change of flexural deformation, additional moment will be aroused and the horizontal bearing behavior of the single pile is influenced. The bearing behavior of the single pile under the combined vertical and lateral loads in sandy soils is studied through indoor model tests. The results show that the horizontal bearing capacity of the single pile increases with the increase of the pre-applied vertical load in sandy soils, which is contrary to the horizontal displacement. The lateral friction resistance in the upper part of the pile decreases with the increase of the horizontal load, while the resistance at the pile end increases actually, and as a whole, the vertical bearing capacity of the single pile decreases in sandy soils with the increase of the pre-applied horizontal load. The depth of the maximum moment caused by the horizontal load is about 5 to 7 times the diameter of the pile, and the influence depth of bending moment along the pile and lateral friction resistance caused by the lateral load is about 10 times the diameter of the pile below the surface of sandy soils. Based on the relevant current research results and theoretical analyses, the interaction mechanism of the components of combined vertical and lateral loads of the single pile in sandy soils is analyzed, and the rationality of the test results is verified.