Stability of Colluvial Slopes

本研究计划探讨建立在崩积层上的天然及人造斜坡的不稳定性。（积土层由残留土壤和迁移土壤混合而成。）当这种材料是斜坡的一部分时，由于重力引起的持续下坡运动，混合物持续处于接近破坏状态。由于崩积层是一种非常常见的地表沉积物，这种破坏模式对建立在这种材料上的大量天然和人造斜坡的形成、运行和/或扩展具有重要意义。这种不稳定的例子包括1996年3月俄亥俄州135英亩垃圾填埋场的边坡破坏——这是城市固体垃圾填埋场中最大的边坡破坏——以及1981年9月圣路易斯大坝上游的边坡破坏。根据这些和其他最近的历史案例，似乎排水的残余抗剪强度可以在天然和人造斜坡下的粘性崩积材料中调动起来，其不利影响是需要更平坦的边坡来设计防止破坏。这导致天然斜坡的发展面积缩小，而堆填区的空间或容量也会减少，因为扩建工程受到限制，或需要花费昂贵的费用从扩建区及/或现有废物的下方挖掘积土。该项目包括实地案例历史研究以及分析和实验技术的结合。该项目的目标是为建立在崩积层上的天然和人造斜坡的建造/扩建提供设计建议。

This research program addresses the instability of natural and man-made slopes founded on colluvium. (Colluvium consists of a mixture of residual and transported soils.) When this material is part of a slope, the mixture is continually in a near-failure state because of constant downslope movement caused by gravity. Since colluvium is a very common surficial deposit, this failure mode has important implications for the creation, operation, and/or expansion of the large number of natural and man-made slopes that are founded on this material.Examples of such instability include the March 1996 slope failure of a 135-acre landfill in Ohio -- the largest slope failure ever in a municipal solid waste landfill -- and the upstream slope failure of the San Luis Dam in September 1981.Based on these and other recent case histories, it appears that a drained residual shear strength can be mobilized in cohesive colluvial materials underlying natural and man-made slopes, with the adverse effect that a much flatter slope is required to design against failure. This results in a smaller area for development in natural slopes and reduced airspace or capacity in landfills, either by limiting the expansion or requiring the expensive excavation of colluvium from the expansion area and/or from under the existing waste.The project includes a study of field case histories and a combination of analytical and experimental techniques. A goal of this project is to develop design recommendations for the construction/expansion of natural and man-made slopes founded on colluvium.