DISCRETE ELEMENT METHOD FOR SIMULATING BALLAST SHEAR STRENGTH FROM LARGE SCALE TRIAXIAL TESTS

摘要

Railroad ballast layer consists of discrete aggregate particles and the Discrete Element Method (DEM) is the most widely adopted numerical method to simulate the particulatenature of ballast materials and their particle interactions. Large scale triaxial tests performedin the laboratory under controlled monotonic and repeated loading conditions are commonlyconsidered as the best means to measure macroscopic mechanical properties of ballastmaterials, such as strength, modulus, and deformation characteristics, directly related to loadcarrying and drainage functions of ballast layer in the field. This paper describes a DEMmodeling approach of railroad ballast with realistic particle shapes developed from imageanalysis to simulate large scale triaxial compression tests on a limestone ballast material. Theballast DEM model captures the strength behavior from both the traditional slow and rapidshear loading rate type monotonic triaxial compression tests. The experimental studyindicates that the shearing rate has insignificant influence on the results of triaxialcompression tests. The results also show the “incremental displacement” approach capturesthe measured shearing response yet can save significant computational resource and time.This study has shown that the DEM simulation approach combined with image analysis hasthe potential to be a quantitative tool to predict the ballast performance.