Construction Technology of Vanguard Fastening System for Short Sleeper Track
It is a universal problem on vibration and noise generated by subway when driving in all countries in the world. Excessive vibration and noise can have a seriously affect on the residents nearby to work and rest, reduce work efficiency, endanger physical and mental health. As we know, subway lines often inevitably pass through areas such as commercial downtown areas, residential areas, cultural and educational health areas, and especially these areas that require high vibration and noise control such as special residential areas, hospitals, schools, concert halls, etc. So people must adopt the measures of vibration and noise reduction to control it so as to meet environmental requirements.
New type of vanguard fastening system can be used for short sleeper buried track bed in order to fit for the above requirements. It is the first time in China for the city subway track engineering project.
Vanguard Fastening System
Working principal of vanguard fastening system
In order to reduce the vibration generated by the track bottom, there are two kinds of methods commonly used in track design in sensitive areas of vibration and noise in today's world: First, improve the quality of the support structure of the elastic track; second, reduce the stiffness of the support structure.
The smaller the stiffness of railway track is, the lower the resonance frequency of the surrounding environment is, and then the better the effect of vibration reduction is. In the past, although the vibration and noise reduction system used lowered vibration and noise, it also brought about greater vertical displacement and produced unacceptable lateral movement of rail head.
Vanguard fastening system is patented by Pandrol Company of the United Kingdom. Compared with traditional rail fastening system, it has the biggest difference that the bottom of steel rail is always in the suspended state through the elastic part (rubber wedge) by supporting rail head and both sides of rail web. Traditional fastening systems usually fastens rail bottom to achieve horizontal position control.
The use of this feature can form a smaller dynamic stiffness. When the trains pass through, the vertical displacement will be more than 3mm in order to achieve efficient of vibration and noise reduction.
Vanguard fastening system is allowable for large vertical displacements of the track. Although the system is also an elastic structure in transverse direction, compared with traditional fastening systems, its interaction with rail wheels is much closer to the wheel-rail contact line, minimizing the twist of steel rail.
(Click→You may want to know more about railway fastening system.)
Structure of vanguard fastening system
Vanguard fastening system includes two types: the bottom plate type and the embedded type. Both types have a very low stiffness and achieve efficient vibration reduction effect. Main components of the embedded type of vanguard fastening system included: rubber wedge, side guard, cast iron locking wedge, retaining shoulder, locking clip, serrated adjustable washer and collision pad. Main components of the bottom plate type of vanguard fastening system are: rubber wedge, side guard, cast iron locking wedge and movable shoulder. In China, on Guangzhou subway line vanguard fastening system was adopted. For the installation and removal of vanguard fasteners, workers must use special tools to finish them.
Main technical specification and advantages of vanguard fastening systemA. Main technical specification
- a. The vertical anti-climb resistance of per fastener is 7 kN
- b. The adjustment range of the fastener height is 0-15mm, and the designed elastic range is 3mm;
- c. The adjustment range of rail gauge is ±20mm (Within the fastener system: ±5mm; bottom plate: ±15mm).
- a. The function of the vibration and noise reduction is equivalent to that of rubber floating plate, and the cost is much lower than that of floating plate system.
- b. The replacement of all the components is simple and easy, which is conducive to the regular maintenance and adjustment.
- c. The construction method is simple and close to common fasteners, and the construction speed is much faster than the rubber floating plate.
Construction Technology of The Bottom Plate Type of Vanguard Fastening System for Short Sleeper Monolithic Track Bed
The assembly of track panel of vanguard fastening system is very vital for railway construction. The assembly of common fastening system is generally with good integrity, and its relative position will not get easily changed. However, for vanguard fastening system, the direct contact position with the rail is the elastic wedge with a 10mm clearance at rail bottom. Special rail sleeper for single vanguard fastening system is 112.8kg in weight. Thus, when rail short sleepers are laid in right places well, before pouring the track bed, the sleepers together with vanguard fastening systems will fall down along with the bottom plate, resulting in a clearance of 40mm. In normal state it only reaches 10mm. This will bring the difficulties to normal construction of track bed.
In this case, if pouring supporting posts of concrete track bed, when people remove the rail supporting frames, the rail surface will greatly sink. Through the analysis, it is believed that this problem can be solved by increasing the overall rigidity of the vanguard fastening system, short railway sleeper and steel rail. Then the stagger joint pad is developed with strong adaptability so as to keep track bed in the better state. This is to mainly use screw spikes to fasten rail bottom by use of self-developed 8mm thick of step plate between the spike and steel rail. The step plate is diagonally arranged on the sleeper. This can increase the joining rigidity of the sleeper and the rail, thereby ensuring the elevation and stability of the rail.
The track panel of vanguard fastening system is assembled on the worktable of ground rail laying base. According to gauge, supporting block spacing, supporting block type, joint intolerance and 25m rail position the track section listed, people can smoothly work on.
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