Many studies describe soil samples by their grain/particle size distribution (GSD/PSD). Most samples are poly-disperse collections of solids. The paper reviews earlier methods to describe or 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 has a R² value typically over 0.999. When remolded soil samples are taken in boreholes, information on stratification is lost, but the MDM recovers information. The MDM improves the prediction of field permeability in stratified soils, which is vital for groundwater and pollution studies. Single layers in stratified soils are unimodal, with a single population of grains. Multimodal soils are either homogeneous (till, crushed stone) or stratified (sandy aquifers). Many borehole samples have up to four modes in their GSDs. The paper gives examples of MDM for six GSDs and presents new findings for three types of sand deposits. For example, it is found that if a sand sample has a coefficient of uniformity, C_U, higher than 3, the sand is stratified. By extracting more information from a GSD, the MDM helps to better evaluate material properties and also sites for their geotechnical and hydraulic properties.

许多研究通过颗粒/粒度分布 (GSD/PSD) 来描述土壤样品。大多数样品是固体的多分散集合。该论文回顾了早期描述或拟合 GSD 的方法：通常，它们的R ²值在 0.5-0.9 范围内。开发了一种模态分解方法 (MDM)，以从 GSD 中提取其亚群或模态、比例和比表面积。这个新的 MDM 易于在电子表格中使用，并且具有R ²值通常超过 0.999。当在钻孔中采集改造土壤样本时，分层信息会丢失，但 MDM 会恢复信息。MDM 改进了分层土壤中田间渗透率的预测，这对于地下水和污染研究至关重要。分层土壤中的单层是单峰的，具有单一的谷物种群。多峰土壤要么是均质的（碎石、碎石），要么是分层的（砂质含水层）。许多钻孔样品在其 GSD 中具有多达四种模式。本文给出了六个 GSD 的 MDM 示例，并介绍了三种类型的砂矿床的新发现。例如，发现如果沙样具有均匀系数，则C _U，高于3，砂层分层。通过从 GSD 中提取更多信息，MDM 有助于更好地评估材料特性及其岩土和水力特性的站点。