# Effect of Track Irregularities on the Response of Two-Way Railway Tracks
## 5 Conclusions  
A 3D finite element coupled train-track-soil model is used to predict ground vibration. This study focuses on vibrations radiating from one track and its effect on the nearby track response. At first, the sub-modeling technique is adopted to model the coupled train-track-soil model. The ground, ballasts and sleepers are represented by 3D solid elements and rails on both tracks are modeled by Euler's beam. The train model and tracks are coupled through dynamic interaction forces between wheels and rails. Finally, a stepwise numerical procedure is used to solve the train-track-soil system. A detailed parametric study is conducted to investigate the influence of track irregularities on the two-way tracks responses at different speeds of the trains. The following conclusions are drawn from the present work.  
1. When the train is moving on one track, the vibration increase as the train speed increases and the track conditions change from good to worse due to track irregularities.
2. The speed of the train has a significant effect on ground vibration. For a given track condition, an increase in speed (when train is moving on one track) causes an increase in ground response as well as shift the response spectra towards high-frequencies e.g., for train speed of 30 m/s the peak appears at 2.9 Hz, whereas it is around 5.7 Hz for 60 m/s.  
Figure 11: **(left)** Time history of ground acceleration at the center of right track at different speeds (trains on both tracks moving in opposite direction) (**a**) speed = 30 m/s (**c**) speed = 60 m/s, (**right) Frequency spectra of ground acceleration at the center of right track at different speeds (trains on both tracks moving in opposite direction) (**b**) speed = 30 m/s (**d**) speed = 60 m/s.  
3. The waves propagating due to moving trains on one track have a great influence on a nearby track. When trains are moving on two adjacent tracks the ground vibration induced by each track causes deformation in the tracks. These deformations in the tracks increase the level of track irregularities which consequently cause an increase in impact forces due to the interaction of moving train and track. Based on the results, it is concluded that the response of a track can increase up to 30% when trains are moving on both tracks.
4. The tracks have shown significantly different responses when trains are moving on two adjacent tracks. At the speed of 30 m/s a series of low-frequency peaks appear in response spectrum, whereas at speed of 60 m/s the track response spectrum not only exhibits peaks at low frequency but also at high frequency (up to 33 Hz). This significant change in track response is due to the wave propagation from one track to the other track.
5. Further studies are needed on the mitigation of track vibration so that a track does not get affected by ground vibration induced by the nearby track.  
[PERSON] supervised the research and helped in review & editing the manuscript. [PERSON] conceptualized the idea, performed the numerical simulation and wrote the manuscript. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.