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通过室内模型试验，研究了砂土和软粘土两层地基的承载力和变形特性。通过量纲分析，得到了可能直接影响这些现象的无量纲参数。试验分为两个系列。一种是采用条形基础和圆形基础在恒定加载速率下进行的承载力试验，另一种是采用圆形基础在小于其承载力的恒定荷载下进行的固结试验。试验均在100 g、等厚度莱尔层下进行，随砂土厚度与基础宽度之比H/B变化。(1)归一化承载力2 qf/γ B是H/B和pO/γ B的函数，其中γ是有效容重，cu是下伏粘土的不排水抗剪强度，cu/γ B是粘土的归一化承载力，pO/g B是归一化上覆压力。在H/B不变的情况下，2 qf/γ B随cu/γ B和pO/γ B线性增加。(2)双层地基的承载力随着H/B的增大而增大，直至达到均匀无限大砂土层的承载力。在无限大砂土中，承载力恒定的H/B值（H/B）** 对于圆形基础约为1.5至2，对于条形基础约为4。(3)两层土的破坏机制可分为两类：一类是（H/B）** 时发生的砂层一般破坏，另一类是H/B小于（H/B）** 时在基础下形成砂块的冲切破坏。(4)双层土在恒载作用下的固结度随强度的增大而增大。在H/B为1.0 ~ 2.0的地基中，荷载强度与承载力之比与固结沉降量之间存在单一的关系。

Centrifuge model tests were carried out to investigate bearing capacities and deformations of two layred soil in whicha sand oelies a relatively soft clay. Non-dimensional parameters which might directy influence on these phenomena were derived from dimensional analysis. Centrifuge tests were divided into two series. One is bearing capacity tests which were conducted under constant loading rate by using strip and circular footing, and the other is consolidation tests in which model grounds were subjected to a constant load less than its bearing capacity through a circular footing. All test were conducted under 100g and constant thickness of clay laer varying with ratios of the thickness of sand to the footing width, H/B.Following conclusions are derived from this study.(1) Normalized bearing capacity, 2qf/ gammaB, is found to be a function of H/B, and pO/ gammaB, where gamma is effective unit weight, cu the undrained shear strength f underlying clay, cu/ gamma B normalized bearing capacity of clay and pO/gB normalized overburden resssure. The 2qf/ gammaB increases linearly with cu/ gammaB and pO/ gammaB under constant H/B.(2) The bearing capacity of the two layred soil increases with H/B until it becomes the bearing capacity of the uniform infinite sand layr. The value of H/B over which the bearing capacity is constant in that of the infinite sand, (H/B)**, is about 1.5 to 2 for circular footing and 4 for strip footing.(3) Failure mechanisms of the two layred soil can be classified into two categories ; one is general faiure in sand layr which occurred for (H/B)** and the other is punching failure forming a block of sand beneath the footing for H/B smaller than (H/B)**.(4) Consolidation of the two layred soil under constant load increases with its intensity. A single uique relationship was found between the ratios of applied load intensities to beaing capacities and consolidation settlements in the grounds with H/B of 1.0 to 2.0.