Evaluation of the Geosynthetic Reinforcement on Railroad Subgrade

Abstract

In recent decades the use of high speed trains increased and it is necessary to consider the demand of High Speed Rail Lines (HSRL) on the infrastructure. Comparing with the conventional rail lines, HSRL can potentially cause greater vibrations which can impact the ballast and foundation layers negatively. This paper aims to investigate how a geosynthetic reinforcement layer may affect the fundamental properties of the railroad subgrade such as the static and cyclic shear strength, sub-ballast layer thickness, and vibration properties. Conducting an experimental program, the shear strengths of the various unreinforced and reinforced soil samples were determined by use of the Simple Shear Test and then, a certain percent of the shear strengths were used as the cyclic loads in the Cyclic Simple Shear Tests. It is shown that the inclusion of geosynthetic in sub-ballast layer improves its strength properties. The results approve that the reinforced layers by geosynthetics have more resistance against static and cyclic loads. It is also observed that the reinforcement has a remarkable effect on the reduction of settlement. The results also reveal that the reinforced samples by G1 and G2 have higher cyclic shear strength while G3 is more effective under static loads but has no remarkable influence under cyclic loads. As a result it can be said that the cyclic behaviour cannot be modelled by just conducting a static test.