Many studies describe soils by their grain/particle size distribution (GSD/PSD). Most samples are poly-disperse collections of solids. A companion article has reviewed earlier methods to fit a GSD: usually, their R² value is in the 0.5–0.9 range. A modal decomposition method, MDM, was developed to extract from a GSD its sub-populations or modes, proportions, and specific surface area. This new MDM is easy to use in a spreadsheet and yields a R² value typically over 0.999. This article explores the MDM potential for future research in engineering geology. Examples are provided for the accurate mathematical description of the GSD, instead of using a few parameters and adjectives. For stratified formations, the MDM found that their sub-layers respect the usual filter criteria for well-graded or 1-mode soils. For internal erosion, the MDM has made it clear that the usual criteria are not enough and two new criteria seem to be needed, about the d-length over which the GSD slope criterion is not respected and its position. These new results should interest many researchers. In short, the MDM appears as a promising and useful tool for future research in engineering geology because it gives a close-to-perfect fit for the GSD, has the capacity to better define quantitatively a GSD, the capacity to better understand and define the conditions for filtering actions, and for the risk of internal erosion.

许多研究通过颗粒/粒度分布 (GSD/PSD) 来描述土壤。大多数样品是固体的多分散集合。一篇配套文章回顾了早期拟合 GSD 的方法：通常，它们的R ²值在 0.5-0.9 范围内。模态分解方法 MDM 被开发用于从 GSD 中提取其亚群或模态、比例和比表面积。这个新的 MDM 很容易在电子表格中使用，并产生一个R ²值通常超过 0.999。本文探讨了 MDM 在未来工程地质研究中的潜力。提供了 GSD 准确数学描述的示例，而不是使用一些参数和形容词。对于分层地层，MDM 发现它们的子层遵守通常的分级良好或 1 模式土壤的过滤标准。对于内部侵蚀，MDM 已经明确表示通常的标准是不够的，似乎需要两个新的标准，关于d- 不遵守 GSD 斜率标准的长度及其位置。这些新结果应该引起许多研究人员的兴趣。简而言之，MDM 似乎是未来工程地质研究的一个有前途和有用的工具，因为它几乎完美地拟合了 GSD，有能力更好地定量定义 GSD，能够更好地理解和定义 GSD过滤作用和内部侵蚀风险的条件。