层状地基中水平受荷桩-土相互作用试验

为了深入研究侧向受荷桩的承载特性及抵抗变形的能力，结合实际工程中天然土体的成层特性，开展了侧向受荷桩的室内模型试验，研究了不同粒径土层厚度及相对密实度对桩土相互动态耦合作用的影响，并结合PIV图像技术，分析了桩周土体位移场的发展趋势，为水平受荷桩的设计提供了理论依据。试验结果表明：①土体刚度与较小粒径土层的厚度呈正相关关系，而较大粒径砂土层厚的增加则对整个桩土体系的刚度产生了弱化作用；②当桩顶位移相同时，随着较小粒径砂土层厚的增大以及相对密实度的提高，土抗力随之增大，在深度为5~6倍桩径范围内达到最大值，且相对密实度对土抗力的影响更大；③水平受荷桩的桩前和桩后砂土表面均形成了一个纺锤形的位移影响区域，且此区域与水平加载方向的最大夹角随土层条件和相对密实度的变化很小，其值均为45°左右；④在相同的桩顶荷载下，砂土相对密实度的增大约束了桩体的运动趋势，使得桩体的水平位移减小，例如，当桩顶荷载均为30 N，密实度为0.5时桩前砂土的最大位移影响范围比密实度为0.3时普遍减少了约1倍桩径的距离；⑤桩身弯矩值随着较小粒径土层厚度的增大而增大，最大弯矩约出现在0.15 m深度（5倍桩径）处；随着砂土相对密实度的提高，桩身弯矩也逐渐增大，最大弯矩所在的位置逐渐上移。

Experimental Study on Pile-soil Interaction Under Horizontal Load in Layered Foundation

To further study the bearing characteristics and deformation resistance of laterally loaded piles, an indoor model test on laterally loaded piles was carried out considering the layered characteristics of a natural soil in practical engineering. The effects of thickness and relative compaction of the layered soil on the dynamic coupling between the piles and soil were studied. The development trend of the soil displacement field surrounding the piles was examined in conjunction with PIV image technology, providing a theoretical basis for the design of laterally loaded piles. The test results showed that:① The stiffness of the soil rises as the soil layer with smaller particles becomes thicker. Conversely, when the thickness of the sand layer with larger particles grows, the stiffness of the entire pile-soil system decreases. ② When the displacement of the pile top remains unchanged, the soil resistance increases with the thickness of the sand layer with smaller particle size and relative compaction. At around five to six times the diameter of the pile, soil resistance reaches its maximum value, and relative compaction has a greater influence on soil resistance. ③ A spindle-shaped displacement area is formed on the sand surface before and after the horizontal loading of the pile, and the maximum angle between this area and the horizontal loading direction changes slightly with soil conditions and relative compaction. ④ Under the same pile top load, the increase in the relative compaction of sand restricts the movement trend of the pile and reduces its horizontal displacement. When the load on the top of the pile is 30 N, for example, the maximum range of sand movement in front of the pile is approximately one-times the diameter of the pile less when the relative compaction is 0.5 than when it is 0.3. ⑤ The bending moment of the pile increases with the increase in thickness of the soil layer with smaller particle size, and the maximum bending moment occurs at a depth of 0.15 m (5 times the pile diameter). With the increase in relative compaction of the sand, the bending moment of the pile increases gradually, and the position of the maximum bending moment moves gradually up.