In order to clarify the bearing mechanism of closed-ended and open-ended piles supported by a thin bearing layer, pile-loading tests are conducted on model grounds with different bearing layer thicknesses, and the soil deformation characteristics around the pile tips are observed by X-ray micro CT. In the case of open-ended piles supported by a thin bearing layer, the soil in the pile greatly displaces following the downward displacement of the soil located more deeply than the pile tip, and the soil density in the pile becomes lower than when the bearing layer thickness is sufficiently large. These characteristics probably cause lower inner friction and lower base resistance, resulting in a lower bearing capacity. When the bearing layer thickness is more than three times the pile diameter, the bearing capacity is much higher than when the bearing layer thickness is the same as the pile diameter. In addition, soil deformation which occurs is almost entirely in the bearing layer, and the changes in bearing capacity are hardly affected by the soft layer below the bearing layer. The experimental findings obtained in the present study support the idea that the criterion for the bearing layer thickness, where the influence of a thin bearing layer on the bearing capacity can be ignored, is three times the pile diameter, regardless of whether the pile tip is open or closed.

为明确薄承重层封闭桩和敞口桩的承载机理，在不同承重层厚度的模型地基上进行桩载试验，观察桩尖周围土体变形特征： X 射线微 CT。承重层较薄的开口桩，随着比桩尖更深的土体向下位移，桩内土体发生较大位移，桩内土体密度比承重时低。层厚度足够大。这些特性可能会导致较低的内摩擦和较低的基础阻力，从而导致较低的承载能力。当承载层厚度大于桩径的三倍时，承载力远高于承载层厚度与桩径相同时的承载力。此外，发生的土体变形几乎全部发生在承载层中，承载力的变化几乎不受承载层下面的软层的影响。本研究中获得的实验结果支持这样的观点，即无论桩尖是否为桩端，其承载层厚度的标准是桩径的三倍，即薄承载层对承载力的影响可以忽略不计。打开或关闭。