Hottest rail embedded track structure

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Rail embedded track structure in order to reduce track settlement and maintenance costs, ballastless track has been used to replace the traditional ballasted track system in high-speed railway and heavy haul lines. Rail embedded track structure is a new ballastless track system developed by Holland railconsult company and used in soft soil areas. This structure is composed of continuous concrete box girders laid on the ground. The track is directly fixed on the concrete box girder, as shown in Figure 1. The track structure conforms to the principle of gravity balance: the weight of the structure shall not exceed the weight of the excavated soil, so as not to increase the dead load of the structure. The steel rail embedded track structure has great rigidity, which can reduce uneven settlement and vibration

Fig. 1 the cross section of the rail embedded track structure is a trapezoidal box girder

. From the perspective of geotechnical technology, the goal of rail embedded track is to study the feasibility of building a railway in soft soil areas with low bearing capacity, and to detect the impact of train periodic load

holland railconsult, in cooperation with the Netherlands railway infrastructure authority (prorail), betuwe railway management group, van hattum &blankevoort, Voest and edilon, has laid a 200m long steel rail embedded track test section on the heavy haul line of Rotterdam port railway. The cross section of its box girder bearing structure is trapezoidal, as shown in figure 1

the rail embedded track structure is composed of voest54e1 rail fixed on the edilon embedded track system. Most of the soil under the test section is clay, which is in line with the application scope of 4. Rail embedded track structure during operation

the test track shall be continuously monitored for 18 months after laying. The monitoring contents include: the vertical displacement of the track and the 20m deep soil mass at the lower layer, the acceleration, the degree and pore water pressure of the electronic universal testing machine, as well as the long-term deformation and deformation confirmation when the train passes through

after five years of service, the settlement and performance of the structure were evaluated. The results showed that the concrete structure and embedded track system did not deteriorate. The widest joint of the track bearing structure (the joint formed by pouring) is less than 0.1mm, which is acceptable, and it is expected that the joint will not expand

Figure 2 no deterioration of concrete structure and embedded track system

in addition to structural performance, the settlement and uneven settlement of track structure shall be monitored. As expected, the total settlement of the test site in the past five years was 2cm, which was very small. The differential settlement of this structure is far lower than that of ordinary track, which can not only meet the requirements of ordinary railway line selection, but also meet the requirements of high-speed railway line selection. Although heavy haul trains are operated, the test line does not need frequent maintenance

The trapezoidal box girder structure of the

test line comes from the construction method of cutting, that is, excavate the trapezoid on the subgrade first, and then embed the trapezoidal box girder structure. To pave a 200m test track with this method, only a 2.6m wide supporting structure is required. The surface elevation of the embedded track of the steel rail at the test site is higher than the surrounding soil, which has an adverse impact on the balance principle of electronic limit protection force

later, this excavation concept was further developed, that is, the trapezoidal shape was upside down. In the optimization design, the bearing structure only has two supporting walls instead of four supporting walls, and the foundation is widened to 4m. As the gravity balance is improved and the stiffness is further increased, it is expected that the design optimization of this slab track can limit the total settlement of 100 years to 30mm. It can be seen that it can be applied to various modern high-performance railways

the test shows that the slab track is suitable for railway on soft soil foundation. This concept comes from a new railway construction method, that is to make the seamless continuous support structure connect the upper structure and the lower structure like a large foundation, which has high stability. (end)

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