Study on Three-dimensional Bearing Capacity on Level and Slope Grounds

为了研究水平和边坡基础上有限长度基础受荷载时破坏面和极限承载力（qu）的三维特性，提出一种实用的稳定性分析设计方法，通过改变基础尺寸比（eta=B/L）和基础在基础上的位置，对砂土基础进行了室内荷载试验。在水平地基加载试验中，随着eta的增大，砂土地基的q值逐渐减小，其形状因子（s=q_3/q_2=1+neta）为n=-0.2 ~ -0.5，与其他试验结果吻合较好。另一方面，在粘土基础中，随着eta的增加，q值也随之增加，与分析结果相似，但n值差异较大。在砂土边坡加载试验中，与水平场地不同，随着eta的增加，qu值也随之增加，但随着离坡肩距离的增加，qu值向水平场地呈逐渐变化的趋势。与计算结果相比，qu的测试结果在eta<0.5范围内符合良好，但在eta接近单位（方形基础）时显示出相当小的值。在砂体加载试验中，通过在砂层之间设置黑色细条纹，成功地观察到砂体的破坏面，并用对数螺旋曲线对其进行了精确的数学近似。将已提出的水平地基的三维切片承载力分析方法推广到斜坡地基、倾斜各向异性地基以及偏心和倾斜加载条件下的地基承载力分析。将上述试验结果与目前提出的解决方案进行比较，得到了相当成功的结果。

In order to study three-demensional properties of failure surface and of the ultimate bearing capacity (qu), when loaded on bases in finite length placed on level and slope foudations, and to propose a practically useful design method of stability analysis, laboratory loading tests were performed on sand and clay foundations by changing the ratio of base size (eta=B/L) and the position of the base on the foundation.In loading test on level ground, qu-value decreases as eta increases in sand foundations, showing shape factor (s=q_3/q_2=1+neta) of n=-0.2 - -0.5 that is in good agrreement with other test results as pbtained. In clay foundations on the other hand, qu-value increases as eta increases in the similar manner as analytical results, nevertheless n-value showed a considerably large defference.In loading tests on sand slope, qu-value increase as eta increases unlike in level grounds, but the trend of qu showed gradual change to level ground as the distance from the slope shoulder increases. In comparisons with computation, test results of qu were in good correspondence in the range eta<0.5, but showed considerably smaller value as eta approaches to unity (square foundation).In loading tests on sands, failure surfaces were obseved successfully by setting thin dark stripes between sand layrs, and they were to be approximated mathmatically in good accuracy with log-spiral curves.The three-dimensional slice method of analysis of bearing capacity which has already been proposed for level ground was extended to problems of sloping ground, of inclined anisotropic ground, and of eccentric and inclined loading conditions. Quite successful results were obtained by comparing the above test results and solutions so far presented.