Based on the analysis of existing turnouts, this paper introduces the causes and treatment measures of diseases such as side wear of switch rail, fracture of large pad and foundation diseases of speed-increasing turnouts.
Key words: spiral track bed with side grinding pad foundation of turnout switch rail
I. Overview:
As a railway worker, our most important duty is to ensure the safety of passengers and smooth railway transportation. With the development of science and technology and the improvement of people's quality of life, in order to ensure the comfort and speed of the journey, the quality of railway lines must be strongly guaranteed. Combined with the actual situation of our section, the lines are all mountain railways, and they are also one of the sections with the largest traffic volume in the world. With the sixth speed increase and the establishment of the "Eleventh Five-Year Plan" medium and long-term high-speed railway planning network, high-speed train operation has become an inevitable trend. Turnout is the throat of entering and leaving the station, and it is also the connecting part and transition section between the station and the interval line. The quality of turnout will directly affect the running speed and stability of vehicles. However, turnout is the core part of the line, and there are many diseases. Improving turnout quality will be very beneficial to railway transportation. After my practice and study, I have some simple views on the disease and treatment of turnout.
Second, the specific problems and remediation measures
1, screw problems and solutions:
(1) Because the lateral impact force of the lead screw is large, the radius of the guide curve in the turnout area is small, and the lateral impact force of the frog rail guard section is large, when the train passes through the turnout, especially the frog section, the lateral force acting on the rail is too large, and then it is transmitted to the iron pad, and the bolt bears the lateral force, and the bolt bears bending, stretching and shearing at the same time, so the bolt is easy to break.
(2) Assembly defect or manufacturing deviation.
(3) The screw lacks maintenance for a long time. After loosening, it is pulled up, causing water vapor to enter the screw hole and make the screw rust.
(4) The sleeper is suspended or the elasticity of the track bed is uneven. Under the dynamic action of the train, the screw is greatly pulled out. In this case, the screw is constantly pulled out under the action of repeated train power.
(5) When the bolt torque is too large, the internal thread is easy to be damaged.
The above reasons lead to the failure of screws, the damage of the connection between the turnout sleeper and the large backing plate, which makes the large backing plate unable to be firmly fixed on the turnout sleeper, and the structure above the turnout sleeper loses its firm connection under the action of train power, which makes it difficult to ensure the geometric position of the turnout, causing problems such as turnout shaking, etc. In serious cases, it may cause the rail to evert and the train to derail.
To sum up, there is something wrong with the screw, and I think there are the following improvement schemes.
(1) Keep the good geometry of the turnout, minimize the small direction inside the turnout and within the range of 100 meters, keep the frame size of the turnout and the turnout offset, and reduce the lateral force generated by the train passing through the turnout.
(2) Installation of large bolts cannot be hammered. When tightening is difficult, analyze the reasons, correct and then screw in patiently.
(3) Check the screws frequently, and retighten them in time if they are loose.
(4) Oil regularly, at least twice a year, and replace the failed spring washer in time. When injecting oil, the bottom hole of casing cannot be closed and blocked.
(5) Turnouts should be mechanically rammed, empty hanging plates should be removed in time, defective joints should be comprehensively rectified, and welded joints should be polished and leveled to reduce the dynamic action between wheels and rails.
(6) Improve the thread structure and increase the strength.
2. Problems existing in the pad and improvement measures.
According to the field analysis of the fracture of turnout large pad, the main reason for the fracture is the weak bond between iron pad and sleeper. Especially the long pad of the heart rail part is broken badly. This part of the pad is located in the middle of the long turnout sleeper. Under the action of train load, the long turnout sleeper produces a certain deflection, and the long pad is deformed with the turnout sleeper. However, because the pad is not closely attached to the turnout sleeper, the pad is damaged by bending and shearing at the same time.
The welding of sliding bed plate has both design and manufacturing reasons and maintenance reasons. The main reason for manufacturing is that the quality and strength of welded parts are not enough. The reasons for design and manufacture are mainly reflected in the fact that there are many welds on one side of the curve basic rail. The main reason is the high speed and high density when going straight. The straight point rail drives the sliding bed to sink, and the curved basic rail passively exerts the upward force on the sliding bed. High frequency repeated vibration causes more open welding of curved sliding bed plate. From the maintenance point of view, there are many open welds on the front and rear sliding bed plates of the steel sleeper, mainly because the steel sleeper is not easy to be compacted, and it is easy to form hidden pits and hanging plates, which will cause open welds on the sliding bed plates. The damage of turnout pad makes the rail lose its firm connection with the foundation under the rail, and it is difficult to ensure the geometric size of the turnout, thus affecting the driving. Slip-off welding will increase the torque required to pull the switch rail, which may lead to the switch rail being stuck and unable to pull, resulting in serious traffic accidents. Therefore, we must take the following remedial measures:
(1) Strengthen tamping in the turnout area, especially in the middle of the long turnout sleeper in the center of the turnout, so as to reduce the deformation of the turnout sleeper under the train load.
(2) Strengthen monitoring, re-tighten the big screws on the pad in time to keep the pad in good contact with the turnout sleeper.
(3) Replace the pad and large rubber pad under the sliding bed plate in time to keep elasticity and reduce the impact of the train.
(4) Keep the geometric dimension of the turning part and minimize the distance between the switch rail and the sliding table.
(5) The sliding table should be oiled in time to reduce the friction when pulling the turnout rail.
(6) Strengthen the welding quality of sliding table, etc.
3. Problems and solutions of ballast bed and foundation under turnout.
Because it is located in the mountainous area, there are many rainy seasons, the foundation construction under the turnout is difficult, the skylight time is not enough, and the connection between the upper and lower structures is not dense, so the vibration caused by passing trains is great. These diseases and unstable reasons that endanger the ballast bed and foundation will have an impact on driving. In particular, the foundation boils and oozes, forming an empty car, which will cause the car to shake, affect the comfort of passenger trains, and even cause traffic safety accidents in serious cases. The solution is:
(1) Strengthen monitoring to maintain ballast stability.
(2) Regularly measure and observe the deformation of the train under dynamic load and the residual deformation with time, and pay special attention to the repair work.
(3) Pay special attention to the drainage work, adopt good ballast, maintain good drainage performance, and avoid causing a wide range of boiling and mud.
(4) Replace ballast or even waste ballast to keep the ballast bed stable.
(5) Harden the foundation, keep the foundation stable, reduce the maintenance cost and workload, and so on.
4. Influence of train on turnout wear and corrective measures.
The wear of switch point rail can be divided into straight point rail wear and curved point rail side wear, which will bring about driving irregularity, especially the side wear of straight point rail will directly affect the straight passage of high-speed passenger trains, resulting in a decline in driving comfort.
Because of the side wear of bending center rail: the side wear of bending center rail is mostly concentrated at the side turnout where the starting train passes, and the train gradually accelerates after starting. Under the action of wheel and rail, locomotive wheels are twisted with high power, forming a rolling and sliding trend. When the train enters the lateral turnout, the rim is close to the tread arc inside the rail, forming a sliding trend and gradually accumulating, resulting in rail side wear.
Side wear of straight rail: Side wear of straight rail is closely related to turnout structure and maintenance state. The switch rail is a rail with variable cross-section, and its movable part is supported on the sliding bed and connected with the sliding bed without fasteners. The upper part of the switch rail is close to the basic rail, and the top iron is arranged in the middle of the switch rail, which is against the basic rail. This structure leads to the low linear stiffness of the turnout switch part and the relatively loose structure. I think the close contact between the point rail and the basic rail is an important reason for the side wear of the straight point rail. Under the dynamic action of the train, the switch rails with small spacing will form a certain vector. If the head rail is too long, the switch rail will bend to the inside of the line, and if the head rail is too short, the switch rail will bend to the outside of the line. When the train passes, due to the centrifugal force, the friction center rail is squeezed at the place where the center rail is not tight and before and after, resulting in the side wear of the straight center rail. At the same time, the bad track direction before and after the turnout makes the train snake, which is also one of the reasons for the side wear of the straight point rail. The rectification measures are:
(1) Strengthen the monitoring of bending center rail, polish it in time at the initial stage of side grinding, eliminate the directional diseases of turnout as much as possible in the daily maintenance of turnout, reduce the additional stress of switch rail, slow down the development of side grinding of bending center rail, prolong the service life, and lubricate bending center rail when necessary.
(2) Pay attention to the state control of the top iron to ensure that the top iron never breaks. The jacking of the jacking iron will make it difficult for the two motors to stick together, and the switch rail will bend inward, which will worsen the smoothness of the switch rail. When the top rail is separated from the joint, the free length of the switch rail will become longer, the switch rail will move from point to line, and the switch rail and the basic rail will be subjected to increased lateral impact force, so it is difficult to maintain the frame at the turnout position, and the two moving parts will not be closely attached, which will increase the side wear of the rail.
(3) Oil the sliding bed plate of the turnout in time, so as to eliminate the phenomenon that poor oil injection of the sliding bed plate causes excessive resistance of the turnout conversion force, which leads to unstable adhesion of the turnout.
(4) Reduce the occurrence of rail side wear before and after turnout, and eliminate the original track irregularity in time.