SGER: The Elastic Moduli of Soils With Dispersed Oversize Particles

为了计算承受静态或动态载荷的土壤所经历的弹性变形，需要了解弹性模量。尽管土壤对此类载荷的响应可能不能严格表示为线弹性，但基于线弹性行为的解决方案通常用于估计现场的应力或应变。弹性模量通常在实验室中使用圆柱形样品的传统三轴压缩测试来评估。为了获得有意义的测试结果，有必要将样品直径与最大粒径的比率保持在约 6:1 或更大。 对于直径为 2.8 英寸的传统三轴样品，可测试的最大颗粒尺寸为 0.5 英寸。因此，当在传统三轴设备中测试土壤时，通常的做法是去除平均直径大于 0.5 英寸的“过大”颗粒。大于 2.8 英寸的样品可用于三轴测试；然而，这需要使用大型电池和大型加载系统，使得测试过于昂贵且耗时，无法常规使用。 从传统三轴设备测试的样品中去除大于 0.5 英寸的材料将为计算与大岩石颗粒土壤（即冰碛土、残积土和崩积土）中建造的土木工程项目相关的应力和变形提供不可靠的弹性模量值。该提案提出了由 Hashin 开发的一种理论方法，用于计算由含有分散的大刚性颗粒的弹性材料制成的复合材料的弹性模量。 Hashin 方法仅需要了解颗粒周围基质的弹性模量以及复合材料中刚性大颗粒的体积浓度，即可计算混合物的弹性模量。 这项为期一年的探索性调查的目的是通过对土壤（粘土、淤泥和沙子）和分散的超大颗粒（砾石、玻璃珠、沙子）的干燥混合物进行超声波速度测试来评估 Hashin 方法的有效性。此外，岩土工程文献中报道的应力-应变曲线是通过对实验室制备的土壤-大颗粒混合物进行常规静态三轴压缩试验获得的，将用于获得静态弹性模量。 使用超声波速度测量，可以获得实验室动态弹性模量。利用三轴压缩试验的结果，可以获得静态弹性模量。然后将实验室弹性模量与Hashin理论方法预测的弹性模量进行比较，以评估其可靠性。 探索性研究的结果将作为进一步探讨 Hashin 方法有效性的基础，因为该方法适用于具有不同饱和度和异质性土壤基质的土壤超大颗粒混合物。

To calculate the elastic deformation experienced by soils subjected to static or dynamic loads, knowledge of the elastic moduli is required. Although the response of soils to these kinds of loads may not be strictly represented as linear elastic, solutions based on linear elastic behavior are commonly used for the estimation of stresses or strains in the field. The elastic moduli are normally evaluated in the laboratory using conventional triaxial compressive tests on cylindrical samples. For meaningful test results, it is necessary to maintain a ratio of sample diameter to the maximum particle size of approximately 6:1 or greater. For the conventional triaxial specimen diameter of 2.8 in., the maximum grain size that can be tested is 0.5 in. Thus, when soils are tested in the conventional triaxial apparatus, it is common practice to remove "oversize" particles with an average diameter greater than 0.5 in. Samples larger than 2.8 in. can be used in triaxial testing; however this requires the use of large cells and large loading systems, making the tests too expensive and time consuming to be used routinely. The removal of material larger than 0.5 in. from the samples tested in the conventional triaxial apparatus will provide unreliable elastic moduli values for the calculation of stresses and deformations associated with civil engineering projects built in soils with large rock particles (i.e. glacial tills, residual and colluvial soils). This proposal presents a theoretical method developed by Hashin that calculates the elastic moduli of a composite made of an elastic material containing dispersed large rigid particles. The Hashin method requires only knowledge of the elastic moduli of the matrix that surrounds the particles coupled with the concentration by volume of the rigid large particles in the composite in order to calculate the elastic moduli of the mixture. The objective of this one year exploratory investigation is to assess the validity of the Hashin method by conducting ultrasonic velocity tests on dry mixtures of soils (clay, silt, and sand) and dispersed oversize particles (gravel, glass beads, sands). Also, stress-strain curves reported in the geotechnical literature obtained from conventional static triaxial compression tests on laboratory prepared soils-large particles mixtures will be used to obtain the static elastic moduli. Using the ultrasonic velocity measurements, the laboratory dynamic elastic moduli will be obtained. Using the results from triaxial compression tests, the static elastic moduli will be obtained. The laboratory elastic moduli will be then compared with those predicted by Hashin's theoretical method in order to assess its reliability. The results of the exploratory research will be used as a basis to further explore the validity of Hashin's method as it applies to soil-oversize particle mixtures having a soil matrix with varying degrees of saturation and heterogeneity.