The Static and Dynamic Response of Reinforced Ballasted-Track Under High-Speed Train.

Muhammad Burhanuddin, Dr. Eng., Ir. Imam Muthohar, S.T., M.T., IPM

2024 | Tesis | S2 Mag. S. & T.Transportasi

Pengembangan jalur kereta api cepat menghadirkan tantangan karena terbatasnya keahlian dalam pembangunan dan pengoperasiannya. Salah satu faktor yang harus diperhatikan dalam desain adalah beban dinamis yang timbul dari kecepatan kereta. Ketika kecepatan kereta api mendekati kecepatan kritis, amplitudo tegangan dan deformasi pada tanah meningkat akibat meningkatnya kecepatan kereta. Penelitian ini akan menghitung beban dinamis kereta api cepat Indonesia serta mengetahui pengaruh penerapan jalur balas dengan perkuatan aspal dan jalur balas dengan perkuatan Geogrid terhadap respons statis dan dinamis jalur.
Penelitian ini dilakukan dengan menggunakan pemodelan pseudo-analisis menggunakan Plaxis 3D. Desain jalur kereta api mengacu pada desain jalur Kereta Cepat Jakarta-Bandung dengan beban dinamis kereta CR400AF pada kecepatan 360 km/jam. Perhitungan beban dinamis mengacu pada beberapa literatur sedangkan data material struktur jalur KA didapatkan dari hasil uji tanah di Bandung, Jawa Barat serta beberapa literatur dan standar. Penelitian ini fokus pada lendutan yang terjadi pada tiga model jalur kereta api; jalur balas tanpa perkuatan, jalur balas yang diperkuat aspal, dan jalur balas yang diperkuat geogrid.
Model jalur tanpa perkuatan mengalami lendutan paling besar sebesar 4,425 mm, kemudian lendutan jalur yang diperkuat dengan aspal adalah 3,886 mm dan jalur dengan perkuatan geogrid adalah 2,849 mm. Metode perkuatan aspal mampu mereduksi lendutan sebesar 12% sedangkan perkuatan geogrid sebesar 35,6%. Berdasarkan hasil pemodelan, jalur yang diperkuat geogrid memberikan peningkatan kekakuan jalur kereta api dan distribusi beban yang lebih baik, disusul dengan jalur yang diperkuat aspal, yang dibuktikan dengan pengurangan lendutan yang terjadi.

The development of the high-speed railway line presents challenges due to limited expertise in its construction and operation. Engineers often face the condition of lines that must pass through areas with soft soil. Because of its low stiffness, soft soil can cause track deflection, resulting in excessive deflection owing to train weight and speed. One of the factors that must be considered is the dynamic load arising from the train's speed. As the train speed gets closer to the critical speed, the amplitude of the stresses and deformations in the soil increases due to the increased train speed. This study will calculate the overal induced load generated by Indonesian high speed train as well as investigate the influence of implementing asphaltic-reinforced ballasted track and Geogrid-reinforced ballasted track on track static and dynamic response.
This study was conducted using pseudo-analysis modeling approach using Plaxis 3D. The track refers to ballasted track design of the Jakarta-Bandung High Speed Train with the induced dynamic load from the CR400AF train moving at 360 kph calculated using dynamic amplification factor equation from several previous research. Other required data regarding track elements refer to the result of soil investigation in Bandung, west java with approximation based on the CPT interpretation for each soil layer and relevant literature. This research will focus on increasing the track modulus on the superstructure with reinforcing ballast layer. Three models of ballasted track will be modelled: unreinforced ballasted track, asphalt-reinforced ballasted track, and Geogrid-reinforced ballasted track.
The simulation result indicates that the non-reinforced track model experienced the greatest deflection of 4.425 mm while the deflection of the asphalt-reinforced ballast track is 3.886 mm and for the Geogrid-reinforced ballast track is 2.849 mm. The asphalt reinforcement method can reduce the deflection by 12% while the geogrid reinforcement by 35.6 %.  Based on the modelling results, it is found that Geogrid-reinforced ballast provides increased track stiffness and better load distribution, followed by asphaltic-reinforced ballasted track, as evidenced by the reduction in deflection and reduction in subgrade stress.

Kata Kunci : Dynamic load, asphaltic-reinforced ballast, Geogrid-reinforced ballast, subgrade stress, track deflection, static response, dynamic response, finite element model.