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

这项早期的探索性研究奖章(AGERGE)提供了资金，以测试两个关于无量纲颗粒重量对最大、最小和临界状态空洞率的影响的假设。已经证实，沙粒之间的范德华引力近似等于极细沙粒的粒重。对于淤泥大小的颗粒，范德华引力可能比颗粒重量大得多。本研究的一般假设(假设1)是：如果土壤颗粒之间的引力与颗粒的重量相比很大，则吸引力将影响颗粒的致密化和所产生的空隙比。一个更具体的假设(假设2)是，无量纲颗粒重量，Wa=(颗粒重量)/(吸引力)，可以用来表征吸引力对孔隙率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，这些实验改变了无因次颗粒重量，同时测量了选定的理想化土壤(玻璃球)和真正的硅砂的最大、最小和临界状态的孔隙率。由范德华力引起的无量纲重量将通过改变颗粒大小、改变孔隙流体(空气或水)和在土工离心机中旋转土壤来改变颗粒重量三种方法来改变。如果一般假设(假设1)被证明是正确的，那么在实验室中测量的在地球重力下的最大和最小孔隙比(用于计算土壤相对密度的常用ASTM指数测试)将不会直接适用于其他g场中的土壤(例如，土工离心机模型测试)。因此，数百个有价值的土工离心机试验程序所报告的相对密度可能需要修正或重新解释。如果特定的假设(假设2)被证明是正确的，纠正或执行重新解释的方法可能会被阐明。这个项目在颗粒大小效应方面的工作可能会重塑我们对颗粒大小对岩土材料强度和扩张性影响的一般理解；这种理解在建筑、桥梁和其他基础设施的基础设计中至关重要。

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.