An Investigation on Geosynthetics Effects on Railway Track Stiffnes Based on Field Test Results Comparison to Numerical Analisys Results

The undeniable advantages of railway track in comparison to the other modes of transportation have been caused to development of new railways as well as rehabilitation of the old routes all over the world. On the other hand, one of the major concerns in construction of new railway lines and rehabilitation of the old ones on the loose subgrades are arisen from bearing capacity enhancement and control of subgrade settlement in tolerable level. Amongst the various proposed stabilizing methods for railway subgrades including mechanical and chemical methods, utilizing of geosynthetic materials has been grown during the recent decades. Although the considerable amount of positive effects of using of such artificial material will be certainly implemented in increasing ofrailway track stiffness, the stiffness measurement of the stiffened track with geotextile and geogrid material has been investigated in the current study. For this purpose apart of under construction railway route of Ahwaz-Khoramshahrwhich is located on loose clay-siltysubgradehas been selected for field test program. In the mentioned railway line, four different sections with 25 meter length have been selected for stiffness measurement. These four sections have been included of reinforced embankmentwith Geotexstile,Geogrid, Geotexstile/Geogrid and normal embankmentfor comparison purposes. In order to measure the track stiffness in the mentioned sections, the track has been loaded byballast container wagons in full and empty conditions.The measured rail deflections have been substituted in Talbot's equation and the track stiffness in various sections have been calculated and compared consequently.In another part of the study a three dimensional FE model have been developed using PLAXIS 3D code and verified by using the av ailable field test data. The sensitivity analysis on geogrid axial stiffness EA in the model has been shown a 31% increase in track stiffness in the best condition.