Assessment of Lateral Soil Movements under Embankment Loads

回顾了路堤荷载作用下土体的侧移特性，得出了以下结论。(1)泥炭堆积的侧向变形伴随着相当程度的局部排水，即使在淤积阶段也是如此。(2)根据地基的层状性质，路堤趾下侧向位移随深度的分布有很大差异。讨论的情况包括海相粘土层被泥炭或中密砂土或干粘土结壳覆盖。(3)相对软弱的土体，如泥炭或有机粘土，其侧向变形能力随着路堤荷载强度的增大而显著增大。因此，侧向变形监测对于此类软土地基上路堤的稳定性控制是非常有效的。然而，对于相对坚固的土壤，如超固结粘土，就不能期待同样的事情；这是因为它们往往会经历最终的破坏，而没有明显的潜在破坏迹象。分析程序的核心思想是将处理区细分为一类称为宏单元的特殊有限元，以便以一种简单但可行的方式分析局部流向砂井的水以及处理区的整体“平面变形”。在计算上，采用经典砂井问题的特征函数作为基本宏单元的形函数，将其空间平均值作为该宏单元的未知孔压，并结合该单元的未知节点位移，从而实现了这一点。通过厚层海相粘土层上试验路堤的实测，验证了所提出的宏单元法的有效性。

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.