Date on Master's Thesis/Doctoral Dissertation

5-2018

Document Type

Master's Thesis

Degree Name

M.S.

Department

Civil and Environmental Engineering

Degree Program

Civil Engineering, MS

Committee Chair

Ghasemi-Fare, Omid

Committee Co-Chair (if applicable)

Mohsen, J.P.

Committee Member

Mohsen, J.P.

Committee Member

Kim, Young Hoon

Committee Member

Lewis, James

Author's Keywords

finite element analysis; asphalt as alternative subballat; asphalt binder; track modulus; track performance

Abstract

In the last two decades, trains have been developed either to carry heavy weight of cargo or for high-speed rail transport. Nonetheless, track structure, have not been improved adequate to support the extra loads or dynamic vibrations of high-speed trains. As a result, the performance of track will be affected from heavy freight or high-speed trains. In the long term it results in trackbed damage by increasing the subgrade and ballast displacement. Besides, it negatively affects the performance of the locomotives. Therefore, alternative subballast, should be introduced to reduce the stress and deformation of the track under dynamic or heavy loads. Asphalt underlayment trackbed is an alternative solution, which has been applied in many countries. The thickness of the asphalt layer varies from 10 cm to 20 cm, depends on the regulation of each country. In this study Finite Element (FE) Program, ABAQUS, is used to simulate a three-dimensional railway track to predict the trackbed performance. The model is validated through an analytical model and experimental. The validated model then used to determine the effect of different parameters on the stress and displacement increments on the subgrade under a static load. In the next step, the comparison of the granular and asphalt trackbeds displacement has been studied. The numerical model is used to predict the stress-strain and displacement variations on the subgrade while the thickness of the asphalt layer is varied. Results show increasing the asphalt layer from 15 cm to 18 cm significantly reduces the stress and displacement of the subgrade and results in uniform displacement. Furthermore, results show placing the asphalt layer below the subballast is more efficient than above it. And using the theory of Winkley to determine the track modulus, which is one of the important indicator to determine the track performance.

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