The evolution of crushing in granular materials and its influence on their mechanical properties

在静、动荷载作用下，构成柔性路面、堆石料、公路路堤和地基地基部分的颗粒状材料会发生破碎。很少有人知道不同程度的破碎对颗粒材料的工程性能的影响（即水力导电性、剪切强度和弹性模量）。由于持续的破碎，设计结构（如路面的颗粒基层或公路路堤）的原始工程特性将在其工程寿命期间发生变化。原有工程特性的改变可能会影响结构的稳定性，使其变得不安全。因此，有必要了解颗粒材料破碎的演变和力学。为此，我们将：(1)对颗粒物料的破碎演化进行实验室和模拟研究。实验室研究将包括诱导颗粒材料破碎的试验（静态和动态压缩和剪切试验）。这些试验中破碎的演变将通过评估试样中发生的微观结构变化和比较破碎试验前后测量的材料的粒度分布来评估。此外，离散元法（DEM）将用于研究导致破碎的颗粒间力的水平和分布；(2)评价破碎过程对工程性能的影响。将在破碎前后评估的工程性能是：测试颗粒材料的水力导电性，抗剪强度和弹性模量。研究结果将对岩土工程界有价值，有助于更好地设计柔性路面等土木工程结构，并有助于更好地理解公路路堤在破碎作用下的稳定性和沉降演变方式。

Granular materials forming part of the base of flexible pavements, rockfills, highway embankments, and foundations experience crushing as a result of static and dynamic loads. Very little is known about the effect that varying levels of crushing have on the engineering properties of granular materials (i.e. hydraulic conductivity, shear strength, and elastic moduli). Because of sustained crushing, the original engineering properties with which a structure (i.e. a pavement's granular base or a highway embankment) was designed will change during its engineering life. Changes in the original engineering properties could affect the stability of the structure and could make it unsafe. Thus, there is a need to understand the evolution and the mechanics of crushing in granular materials. To this effect we will: (1) conduct laboratory and simulation investigations on the evolution of crushing in granular materials. The laboratory investigation will involve tests that induce crushing in granular materials (static and dynamic compression and shear tests). The evolution of crushing in these tests will be evaluated by assessing the micro-structural changes that take place in the samples and by comparing the grain size distribution of the materials measured before and after the crushing tests. Also, the Discrete Element Method (DEM) will be used to study the level and distribution of the interparticle forces that cause crushing; and, (2) evaluate the changes in engineering properties caused by the crushing process. The engineering properties that will be evaluated before and after crushing are: hydraulic conductivity, shear strength, and the elastic moduli of the granular materials tested. The results of the research will be valuable to the geotechnical engineering community, for the better design of civil engineering structures such as flexible pavements and for a better understanding of the ways the stability and settlement experienced by highway embankments evolve as a result of crushing.