main damage of railway track structure

Railway Line Disease Control and Maintenance

Due to the dynamic action of rolling stock and the influence of natural conditions on the track geometry changes constantly. The roadbed and track bed are deformed at any time, the line equipment is constantly mechanical wear, the maintenance method is improper, and the periodic large and medium repair work can not be carried out in time, which causes many diseases to the railway line. After the train runs, the damage speed of the track structure and its parts is more serious than other deformation. The main damage of railway track structure is line creep, rail and joint parts disease and curve disease.

1. The track is uneven

In the track structure, the gravel bed is an unstable component. The vertical and lateral dynamic elastic deformation and residual accumulation deformation of the track will occur under the unsteady repeated load of the train. These deformations not only affect the smooth running of the train, but also threaten the running safety when the deformation accumulates to a certain limit. In order to keep the track in good condition, the maintenance and repair of the track structure must be carried out frequently.

Type of track irregularity

(1) Uneven level: due to subgrade subsidence, ballast tamping is not solid and other reasons, the rail along the longitudinal uneven subsidence caused by the front and rear uneven level. Under the action of train power, the rail will be lower than the cushion plate, the top surface of the cushion plate and the sleeper and the track bed will appear lifting plate or dark pit, which is very unfavorable to the safety of running.

(2) Uneven level: mainly due to the unequal sinking of the left and right rail

(3) Triangle pit: within a specified distance, first the left rail is higher than the right rail and then the right rail is higher than the left rail, the height difference exceeds the allowable deviation value and the distance between the two maximum horizontal error points is less than 18m. Its existence may make the train in a fixed axle before and after one of the four wheels of the instant load reduction or suspension is serious when it may climb the rail crisis driving safety.

(4) The direction is not smooth: it means that the line is not straight and the curve is not round. It is usually caused by the loosening of the hard-bent fastener of the rail and the poor slope of the softening curve. The bad direction of the line must cause the train wheels to swing from side to side, aggravate the wheel impact and cause other line diseases.

(5) Compound irregularity: refers to the vertical and horizontal irregularity in the same position of the rail.

Measures to rectify the track irregularity

(1) The use of large road maintenance machinery: the works section provides detailed information to the construction unit, such as: comprehensive line drawing, distribution diagram, curve elements, and other machinery according to the above materials to do the track, track tamping and tamping work, and after each operation, carry out the dynamic stability of the ballast bed, supplement the ballast to replace the damaged rubber pad, and remove the operation section to adjust the cushion plate, the pavement of the crossing, and the protection rail on the ballast bridge

(2) Diversion operation: The diversion operation is carried out when the gauge and its change rate are poor, and the diversion of the concrete tie line is achieved by adjusting the fastener or the gauge baffle.

(3) Plate operation: When the deviation of the local high and low level triangle pit of the line switch is small (not more than 6㎜), the track tamping is difficult to meet the operation requirements. Each height plate shall not exceed 3 pieces, and the total thickness shall not exceed 25㎜.

(4) fastener operation: slack fastener will cause the rail to produce local displacement along the sleeper. It is required to keep the fasteners closely in the right state, and generally tighten them again the next day after the plate operation. The fasteners should be fully tightened before and after the maintenance operation.

2. Ballast bed diseases

Track bed is the foundation of track frame. The main cause of track deformation is the deformation of track bed, and the uneven settlement of track driving safety. Therefore, it is necessary to know the cause of the deformation of the track bed and its disease treatment to ensure the smoothness of the line and make the train run safety.

The types of road bed diseases:

Road bed pollution, road bed subsidence, road bed turning

(1) Poor ballast quality

Some of the ballast is limestone material, the strength of the ballast is low wear resistance and impact resistance, poor crushing resistance. Now the railway gradually realizes the heavy load. Under the repeated action of train gravity, the ballast is squeezed and worn together, and it is powdery after wear, which is prone to diseases such as turning and hardening.

(2) Subgrade bed pulping:

① The compactness of the subgrade foundation bed is insufficient, and the particles of the roadbed are embedded into the foundation bed to form a film under the long-term action of the train load, resulting in the surface water being unable to discharge and forming diseases such as puddling water.

② The daily maintenance work will cause the damage of the denomination smoothness of the subgrade, resulting in uneven surface of the subgrade and poor drainage of the subgrade surface.

③ Other causes: the garbage and feces of sand and dust passenger cars seriously pollute the ballast bed, which reduces the water permeability and elasticity of the ballast bed and easily forms diseases such as slab churning.

Improvement of road bed diseases

(1) Strengthen the quality management of ballast bed

① Strictly implement the standards of gravel ballast, control the quality of ballast from the source, and resolutely prevent unqualified ballast from entering the railway line

② According to the actual situation of the ballast, timely line screening and timely replacement of the ballast material does not meet the standard of the ballast completely ballast structure, restore the good condition of the ballast

③ Combined with the maintenance of the flip side slope to clean the sieve and change the water drainage of the track bed to prevent the occurrence of water and other diseases.

(2) Repair machine diseases to restore the compactness and smooth drainage of the subbed, for the subbed filler is poor or insufficient compactness of the subbed caused by the pulping disease should be taken to replace the subbed soil to improve the soil condition of the subbed filler thoroughly restore the road arch to ensure smooth drainage of the subbed surface.

(3) Strengthen the target of operation to avoid damage to the original roadbed surface by maintenance

(4) Improve the external conditions to reduce the pollution of the road bed, strictly recycle the passenger car garbage and unified cleaning at the station, maintain the cleanliness of the road bed, so as to improve the environment of public works and reduce the pollution of the environment.

3. Common diseases of concrete sleeper

Concrete sleeper line and steel rail, concrete sleeper, fastener track bed and other parts. The rail is directly subjected to the huge pressure from the rolling stock and transmitted to the sleeper. The concrete sleeper withstands the vertical and vertical force from the rail through the elastic cushion and the middle fastener, and then distributes the transverse and longitudinal horizontal force on the track bed, and maintains the normal position of the rail. The use of concrete Guizhen in our country has a history of many years, and the experience shows that the use of concrete sleeper plays an important role in strengthening the track structure to ensure the safety of traffic. However, the problems in the design, manufacture and use of the inner sleeper are only partially damaged early, which affects the normal use.

The main damage forms of concrete sleeper

(1) Excessive transverse cracks appear in the lower section of the rail. Concrete sleeper is a member subjected to unstable repeated loads. The variation of the load is random, and the bending moment of the concrete sleeper under the rail may be greater than the cracking strength of the section during the service period. In this case, transverse cracks are created which are generally small enough not to cause the sleeper to fail but in some cases the load moment of the sectional surface is much greater than the cracking strength of the sleeper and then there will be too large transverse cracks causing the sleeper to fail.

(2) Rail cross section collapse:

Under the sleeper part due to rubber plate damage or string out, so that the rail directly acting on the rail groove caused by rail cross section is too large. Excessive pressure in the concrete compression zone is the result of concrete collapse.

(3) Sleeper longitudinal cracks:

Sleeper extension axis of the direction of the cracks called longitudinal cracks generally have the end of the crack on the surface of the crack side horizontal longitudinal cracks, nail holes longitudinal cracks, through longitudinal cracks and other longitudinal cracks more parts are along the bolt hole on both sides or stress reinforcement and to the end and the middle development. The appearance of such cracks will seriously affect the service life of the sleeper.

(4) The crack of the sleeper:

The crack is the small cracks crisscross the surface of the sleeper, which generally occur at the end of the sleeper and the top and side of the middle. Cracking also has a great influence on the service life of the sleeper.

(5) The sleeper shoulder is damaged:

The sleeper shoulder is damaged due to the horizontal thrust from the fastener. Especially on the small radius curve, this phenomenon is very common and the use of widened iron seats still cannot solve the problem. According to statistics, the shoulder break on the curve with a radius of 400m is as high as 70%. In addition, the shoulder break may also be caused by gasket damage or defects in the shoulder stop part during the manufacturing process of the sleeper.

(6) The bottom side of the sleeper block: manual tamping the bottom side of the impact rail makes the concrete block area of up to 100 square centimeters. The result is that the stress condition of the sleeper deteriorates easily and causes various other injuries and weakens the stability of the track.

(7) The middle part of the sleeper is crushed

The middle part of the sleeper due to the force is too large positive bending moment, not only makes the lower part of the middle part of the sleeper produce too large cracks, but also causes excessive compressive stress in the compression zone of the section, resulting in concrete collapse, this situation generally occurs in the rail joint. Some sleepers bear too much negative bending moment in the middle part, which not only causes cracks in the upper part of the middle part, but also causes the lower part of the middle section to be overwhelmed by too much compressive stress, and even the steel bar is exposed.

(8) Longitudinal cracks of sleeper

The cracks along the long axis of the sleeper are collectively referred to as longitudinal cracks. Longitudinal cracks generally have end cracks, end surface cracks, lateral horizontal longitudinal cracks, nail holes longitudinal cracks, through the longitudinal cracks, etc., the more longitudinal cracks are along the sides of the bolt hole or stress reinforcement, and to the end and the middle development. The appearance of such cracks will seriously affect the service life of the sleeper.

(9) Oblique crack and sprain of the middle part of the sleeper

The oblique crack sprain of the middle part of the sleeper refers to the damage in the diagonal direction. The middle part of the sleeper is prone to diagonal crack or sprain due to diagonal tamping on both sides of the sleeper during line maintenance. According to the investigation and statistics, the middle of the sleeper broken or broken because of improper line maintenance occupies a certain proportion in the total number of damaged sleeper.

(10) Corrosion of the sleeper

In the long-term water release area and the vehicle loaded with harmful media scattered on the rail sleeper, will cause the corrosion of the sleeper, light concrete surface pitting, delamination and other phenomena, heavy steel rust, and gradually extend to the inside.

Causes of damage to concrete sleeper:

(1) Manufacturing quality: In the classification of various types of damage of concrete sleeper, longitudinal cracks are the most harmful to driving safety, and once they occur, the development is extremely rapid and serious, causing splits and cracks through the full length of the sleeper. Loose spalling of concrete is the most harmful to the bearing capacity of sleeper to maintain track status and service life, and this kind of damage is generally caused by poor manufacturing quality.

(2) Maintenance and maintenance operations: In the maintenance and maintenance operations, if the stress state of the sleeper changes, the phenomenon of the sleeper section load bending moment greater than the sleeper cracking strength may occur, resulting in the sleeper damage. The impact of maintenance and maintenance operations on the sleeper damage is mainly manifested in the following aspects: The damage of cushion layer and insulation buffer gasket under the rail during tamping operation is not replaced in time. The fault of the track bed is not rectified in time.

(3) Concrete sleeper disease remediation: according to the use of the design of a more reasonable sleeper to improve the reliability of the sleeper structure and high strength sleeper. Be careful not to damage the sleeper as much as possible during maintenance work.

4. Rail joint disease

The rail joint is the weak link of the line, and the concrete sleeper line is more serious. When the wheelset of the rolling stock passes through the joint, it produces violent vibration due to its irregularity, accelerates the change of the state of the line, and causes the joint disease. After the joint disease occurs, it further aggravates the damage effect of locomotive and vehicle wheel pair on the line, mutual cause and effect, so that the development and change of the disease increase. When the status of rail, track bed and subgrade is basically the same, the concrete sleeper line joint changes faster than the wooden sleeper line joint, and the disease period of various joints is short and the development is rapid. If the disease is not fundamentally remedied, it is difficult to maintain the normal working condition of the joint and affect the railway operation.

Rail joint disease classification:

(1) According to the status of the joint rail surface: offset joint, uneven wear joint, wrong tooth joint, metal stripping joint, large rail joint

(2) According to the state of the joint ballast bed: slurry joint, white joint, sliding joint, hard joint

(3) According to the structural state of the joint: the lower bending of the joint splint, the upper edge of the abrasive splint bolt nut torque is insufficient; Fastener nut torque is insufficient, fastener plate or gauge baffle is not tight, fastener failure, etc.

Causes of rail joint disease

The most fundamental cause of rail joint disease is the structural irregularity of rail joint, which leads to a large additional dynamic effect between wheel and rail. The excessive additional dynamic effect also promotes the development of irregularity and the growth of additional dynamic force, and at the same time promotes the development of joint diseases. It can be seen that the occurrence and development of rail joint diseases interact. Due to improper maintenance will also promote the joint disease.

(1) Structural irregularity: the irregularity of the rail joint in the structure refers to the joint rail joint: when the wheel is at the output end of the rail, the receiving end of the adjacent rail has a tendency to raise, forming a step; The deflection of the rail joint under load is not a continuous curve, but a broken line. When the Angle, rail seam, step three factors appear at the same time, will produce wheel-rail impact, thereby increasing the additional resistance at the joint.

(2) Additional irregularity: This is formed in the operation process: the following conditions can be formed: weak structure, uneven wear of the rail surface, insufficient elasticity.

(3) Dynamic irregularity: there are generally two cases: one is uneven track elasticity and load fluctuation, wheel-rail contact point track is wavy irregularity; The other is the existence of dark pit hanging plate and uneven elastic subsidence of ballast bed. The dynamic irregularity of the line aggravates the shock and vibration of the train in operation. Sometimes the use of different thickness, uneven elasticity under the rail plate and the poor maintenance quality of the line aggravate the dynamic irregularity of the track.

Rail joint disease rectification:

(1) Improve rail material, quenching technical requirements, quenching process, rail and splint rated design

(2) In the maintenance and maintenance of the concrete sleeper line to adopt the characteristics of the method to improve the working state of the rail joint, such as: according to the local temperature changes, timely adjust the bad rail joint, maintain the suitable rail joint; Maintain the torque of the joint bolt and fastener, so that the partial connection of the joint is stable; In the joint part of the ballast tamping to ensure good tamping quality; Flat rail treatment should be carried out for the offset joint; The splint with downbend should be replaced with the splint with upbend and shock absorbing splint; It is necessary to pay attention to the repair of the rail surface, and take welding repair, grinding and other ways to repair the defects and diseases such as uneven wear, falling block and abrasion of the rail. Improve the elasticity of the joint part of the ballast, mainly by cleaning the sieve plate knot and turning the ballast, and replacing the rounded stone ballast.

Methods to prevent rail and joint joint parts disease:

Strengthen rail and splint maintenance work

(1) Strengthen rail inspection: found seriously injured rail and splint, should be replaced in time;

(2) Straighten the hard-bent rail in time

(3) Timely welding repair rail surface scratches

(4) Often pay attention to tighten the fasteners, repair the anti-climbing equipment, lock the rail, prevent crawling, and do not make the rail seam bigger.

Intensive joint maintenance

(1) Strengthen the joint tamping, keep the ballast full, and tamp. The material of the joint sleeper is as consistent as possible, and the spacing is in accordance with the regulations to maintain the same supporting conditions.

(2) Tighten the splint bolt frequently to keep the joint strong. Due to the continuous blow of the train, the bolts will be loosened and the joints will be loosened. As a result, the joint cannot resist external forces as a whole, and individual parts may be damaged due to excessive load. At the same time, it will increase the wear of the splint and the rail end and aggravate the joint irregularity. If the gap between the cleat at the joint and the rail jaw due to wear is more than l mm, it should be padded in time to conform to the specified triangular iron sheet.

(3) Clean the unclean ballast within the scope of the screen joint in time, so as not to form a hard shell, lose elasticity, or cause churning and mud, resulting in significant irregularity.

(4) Timely elimination of rail surface high and low teeth, joint rail surface and gauge line inside teeth shall not exceed 1 mm.

(5) Upper bend splint control low joint. The upper bending splint is the general splint bent with the rail bender, and the upper bending amount is generally 1 or 2㎜. When the bending splint is replaced, the rail surface is raised within the range of the 4 sleeper at the rail joint, which is easy to loosen the hanging board and bolts, so it is necessary to strengthen tamping and tighten the bolts.

(6) Adjust the rail seam in time. Large rail joint is an important cause of joint disease. Therefore, the rail seam must be uniform and meet the specified requirements, and the large rail seam should be straightened in time.