Geometric composition, structural behavior and material design for asphalt trackbed: A review

Feasibility Study of a Compatible Design Method for Asphalt Concrete-Based Track Substructure Considering Viscoelastic Properties

“…Since the structural rigidity of the asphalt trackbed is smaller than that of the concrete base, the ability to disperse the dynamic load is weaker. To ensure safety, the formation layer of the AC-based track needs to be strengthened, which can be equivalent to a greater design value than 0.4 m. The results are consistent with the conclusion of related research abroad, which shows that the roadbed under the asphalt trackbed (asphalt overlayment, the AC layer is directly in contact with the slabs, sleepers, or the rails) needs reinforcing soil to ensure the security of the AC-based track ( 7 , 46 ). The reason may be that asphalt concrete, as a flexible material, is greatly affected by temperature.…”

“…Meanwhile, the thickness of the asphalt trackbed was changed to explore the influence on the vertical dynamic stress attenuation in the substructure. Previous research indicated that the thickness of the asphalt trackbed in the railway is applied from 200 to 350 mm ( 7 ), so the thickness varying in this modeling is set as 150, 200, 250, 300, and 350 mm. In addition, the AC-based track with the asphalt trackbed directly in contact with the slabs has never been applied in Chinese engineering, and its structure is distinguished from that of the traditional ballastless track in China.…”

“…This reflects the high modulus of asphalt concrete at low temperatures. However, in an environment with high temperatures, the flexibility of asphalt concrete increases, and as a material with strong temperature sensitivity, fatigue damage caused by temperature can easily occur between asphalt concrete layers ( 7 ). Therefore, the typical representative temperature T 1 = 20°C and the possible high-temperature T 2 = 40°C under direct sunlight in the warm zone were selected as the temperature variables.…”

“…The dynamic stress in the substructure is influenced by numerous factors, such as the train speed or load frequency ( 5 ), external environment and soil conditions ( 6 ), as well as measured location. An asphalt concrete-based track (AC-based track) structure, with the merits of waterproofing and vibration damping as well as environmental isolation, has been used increasingly in more than 14 countries ( 7 – 9 ). The vertical dynamic stress attenuation in railway AC-based track substructure may be different from that in the conventional track as a result of the viscoelasticity of the asphalt concrete.…”

Experimental Analysis of Hot-Mix Asphalt (HMA) Mixtures with Reclaimed Asphalt Pavement (RAP) in Railway Sub-Ballast

“…In the literature, several analytical and numerical models to investigate railway track performance [ 15 ] demonstrated the effectiveness of asphalt layers to increase stiffness and bearing capacity [ 16 ] of the substructure [ 17 ], while the dynamic effects still should be deepened [ 18 ]. Fang et al [ 19 ] identified four asphalt trackbeds (i.e., asphalt underlayment, asphalt overlayment, surface asphalt mixture impermeable, and asphalt stabilized ballast) that differ for functional and structural properties of the bitumen-bound materials. Global experiences demonstrated that the construction of sub-ballast [ 20 , 21 ] is a strategic solution for high-speed and high-capacity lines [ 11 , 22 , 23 ], although it has higher environmental and economic costs [ 24 , 25 ].…”