EAGER: Effect of Dimensionless Particle Weight on Maximum, Minimum, and Critical State Void Ratios

这项探索性研究早期拨款（EAGER）奖为测试关于无因次粒子重量对最大、最小和临界状态空隙比影响的两个假设提供了资金。已经确定，对于非常细的砂，砂粒之间的范德华引力近似等于粒重。对于粉粒大小的颗粒，范德华引力可能比颗粒的重量大得多。本研究的一般假设（假设1）是：如果土壤颗粒之间的引力相对于颗粒的重量是显著的，那么这种引力会影响颗粒的致密化和最终的孔隙比。一个更具体的假设（假设2）是，无因次粒子质量Wa =（粒子质量）/（引力）可以用来表征引力对孔隙比和致密化的影响的重要性。这些假设将通过一系列实验来验证，这些实验在测量选定的理想土壤（玻璃球）和真实硅砂的最大、最小和临界状态空隙比的同时，改变无量纲颗粒重量。由于范德华力引起的无量纲重量将通过3种方法改变：改变颗粒大小，改变孔隙流体（空气或水），以及通过在土工离心机中旋转土壤来改变颗粒重量。如果一般假设（假设1）被证明是正确的，那么在地球重力下在实验室测量的最大和最小空隙比（用于计算土壤相对密度的常用ASTM指数测试）将不能直接适用于其他g场（例如岩土工程离心机模型测试）中的土壤。因此，报告的数百个有价值的岩土离心机测试程序的相对密度可能需要纠正或重新解释。如果特定的假设（假设2）被证明是正确的，则可以阐明纠正或执行重新解释的方法。该项目在粒径效应方面的工作可以重塑我们对粒径对岩土材料强度和膨胀率影响的一般理解；这种理解对于建筑、桥梁和其他基础设施的基础设计至关重要。

This EArly Grant for Exploratory Research (EAGER) award provides funding to test two hypotheses regarding the effect of dimensionless particle weight on maximum, minimum, and critical state void ratios. It has been established that van der Waals attractive forces between sand particles are approximately equal to the particle weights for very fine sands. For silt-sized particles van der Waals attractive forces can be much greater than the particle weight. The general hypothesis (Hypothesis 1) of this research is: if the attractive forces between soil particles are significant compared to the weight of the particles, the attractive forces will affect the densification and resultant void ratio of the particles. A more specific hypothesis (Hypothesis 2) is that the dimensionless particle weight, Wa = (particle weight)/(attractive force), can be used to characterize the importance of attractive forces with respect to their effect on void ratio and densification. These hypotheses will be tested by a series of experiments that vary the dimensionless particle weight while measuring the maximum, minimum and critical state void ratios of a selected idealized soil (glass spheres) and a real silica sand. The dimensionless weight due to van der Waals forces will be varied by 3 methods: changing the particle size, changing the pore fluid (air or water), and changing particle weight by spinning the soil in a geotechnical centrifuge. If the general hypotheses (Hypothesis 1) is proven true, then the maximum and minimum void ratios (common ASTM index tests used to calculate the Relative Density of soil) measured in the laboratory in earth's gravity would not be directly applicable to soils in other g-fields (e.g., geotechnical centrifuge model tests). It follows that the Relative Densities reported for hundreds of valuable geotechnical centrifuge test programs may need to be corrected or re-interpreted. If the specific hypothesis (Hypothesis 2) proves correct, a method for correcting or performing the re-interpretation may be illuminated. This project's work on this aspect of particle size effects could reshape our general understanding of the effect of particle size on the strength and dilatancy of geomaterials; this understanding is of fundamental importance in design of foundations for buildings, bridges and other infrastructure.