Assessment of Lateral Soil Movements under Embankment Loads

本文回顾了路基荷载作用下土体的侧向运动特性，得出以下结论：(1)泥炭质矿床的侧向变形伴随着相当程度的局部排水，即使在堤防阶段也是如此。(2)路堤趾下的侧向位移随深度的分布显著不同，这与地基的层状性质有关。所讨论的情况包括由泥炭或中密度砂或干粘土壳覆盖的海相粘土层。(3)泥炭、有机粘土等较弱土体的侧向变形能力随路堤荷载强度的增加而显著增加。因此，侧向变形监测对于此类软基路堤的稳定性控制是非常有效的。然而，对于相对较强的土壤，如超固结粘土沉积物，则不能期望同样的结果；这是因为他们倾向于经历最终的失败，而没有明显的即将失败的迹象。本文提出了一种新的分析软土地基竖向排沙的方法。分析过程的关键思想在于将处理区域细分为一类特殊的有限元，称为宏观单元，从而可以简单而可行地分析处理区域的局部水流流向沙渠以及整体“平面变形”。在计算上，可以采用经典泄沙问题的特征函数作为基本宏观单元的形状函数，并将其空间平均值作为该宏观单元的未知孔隙水压力，并结合该单元的未知节点位移。通过对一厚海相粘土试验路基的性能实测，验证了所提出的宏观单元法的有效性。

The performances of lateral soil movements under embankment loads are reviewed, and the following conclusions are drawn. (1) The lateral deformation of peaty deposits is accompanied by a substantial degree of partial drainage, even during the embanking stage. (2) The distribution of lateral displacements with depth under the toe of an embankment differs significantly, in accordance with the layered nature of the subsoils. The situations discussed include the marine clay beds overlain by peat or medium dense sand or dry clay crust. (3) The lateral deformability of relatively weak soils, such as peat or organic clay, increases markedly with increasing intensity of embankment loading. Therefore, the lateral-deformation monitoring is very effective for stability control of embankments on such soft foundations. The same thing cannot be expected, however, for relatively strong soils such as overconsolidated clay deposits; this is because they tend to undergo eventual failure without noticeable signs of imminent failure.A new analysis procedure for the soft clay foundation treated with vertical sand drains, is developed. The key idea of the analysis procedure lies in subdividing the treated zone into a special class of finite elements named macro-elements, so that the local water flow towards the sand drains as well as the overall "plane-deformation" of the treated zone may be analyzed in a simple but workable manner. Computationally, this is made possible by adopting the eigen-function of a classic sand-drain problem as the shape function of a basic macro-element, and by taking its spatial average as the unknown pore-water pressure of that macro-element, in combination with the unknown nodal displacements of that element. The validity of the proposed macro-element method is examined and confirmed against the measured performance of a test embankment on a thick bed of marine clay.