A seamless line laying method using middle locking and two-end stretching

Abstract

The present invention belongs to the technical field of seamless track laying, and discloses a seamless track laying method that adopts middle locking and two-end stretching, so as to solve the technical problem of wasting construction windows during the construction process of the existing seamless track laying technology, which is to wait for the welding at the dragon mouth to be completed and locked before stretching and locking at the dragon tail. The method calculates the unit rail section length of the rail according to the upsetting amount and the reserved rail joint, and locks the rail according to the unit rail section length. At the dragon mouth, a welding machine is used to stretch and close the reserved rail joint; then, the upsetting amount is used as the stretching amount to stretch and weld in the direction of the dragon mouth; at the dragon tail, it is stretched in the direction of the dragon tail, and after stretching, it is connected to the existing rail through a splint. In the seamless track laying method provided by the present invention, the length of the stretching amount is first determined, and then the locking position is determined to lock the rail. After the middle position of the rail is locked, it can be stretched in the direction of the dragon mouth and the dragon tail, which can greatly improve construction efficiency and save construction windows.

Description

Technical Field

[0001] The present invention relates to the technical field of seamless track line laying, and in particular to a seamless track laying method adopting middle locking and two-end stretching. Background Art

[0002] CWR rail replacement is a key technology in today's railway track replacement. CWR is a new track structure suitable for heavy-haul trains and high-speed railways. Extensive research indicates that CWR rails can save 35% to 75% in maintenance and repair costs compared to conventional jointed rails, both in terms of labor savings and equipment life extension. Therefore, the development of CWR rail installation technology is currently of paramount importance. CWR rail installation is a complex, systematic project requiring strict adherence to construction standards, strengthened construction management at all stages, the active adoption of scientific and rational construction processes, and the optimization of CWR rail structures. This will ensure continuous improvement in the quality of CWR rail installation and maintenance, fully leveraging its significant advantages and enhancing the economic and social benefits of railway projects. The stability of CWR rail installation depends on the internal thermal stresses and resistances experienced by the rails, including longitudinal and transverse resistances of the trackbed, joint resistance, fastener resistance, and track frame stiffness. When the thermal stresses experienced by the rails are less than or equal to the resistances, the track is stable. Conversely, when the thermal stresses experienced by the rails exceed the resistances, track stability becomes difficult to maintain, and track expansion and runaway are more likely to occur. Therefore, correctly and reasonably setting the locking rail temperature is the prerequisite for ensuring the stability of the seamless line. The locking rail temperature plays a vital role in the stability of the seamless line.

[0003] The rails are then laid in the grooves of the rails, and the rails are stretched from the tail to the tail, and the welding is completed. Summary of the Invention

[0004] In response to the deficiencies in the prior art, the present invention provides a seamless line laying method with middle locking and two-end stretching. After the rail-changing vehicle has laid the new rails, the method calculates the unit rail section length of the rail based on the upset amount and the reserved rail gap, locks the rails according to the unit rail section length, and then stretches them from the locked position toward the dragon mouth and the dragon tail, respectively. This solves the technical problem in the prior art of seamless line laying that, during the construction process, the construction window is wasted and the construction progress is reduced, as the welding at the dragon mouth must be completed and locked before stretching and locking can be performed at the dragon tail.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] A seamless line laying method using middle locking and two-end stretching comprises the following steps:

[0007] S1: Set up signal protection; issue a construction blockade order and start work;

[0008] S2: Overlap the return line at the starting and ending points of the track change section;

[0009] S3: Cut the existing rails; remove the sleeper fasteners of the existing rails in the rail replacement section;

[0010] S4: The rail-changing vehicle operates to change rails, and collects and records the temperature of the rails when they enter the rail-supporting groove and the temperature of the rails after they fall into the rail-supporting groove;

[0011] S5: The rail-changing vehicle moves to the spur hole. After the rail at the spur hole falls into the rail-bearing groove, the stretching amount of the rail is calculated based on the upsetting amount of the welding machine and the reserved rail gap at the spur hole.

[0012] S6: Calculate the length of the rail of the unit rail section according to the temperature of the rail when entering the rail groove, the temperature of the rail after falling into the rail groove, and the stretching amount, that is, the distance between the lead mouth and the locking position;

[0013] S7: Rail position locking; lock from the length of one unit rail section away from the dragon mouth to the dragon tail;

[0014] S8: At the rail mouth, the reserved rail gap is stretched and closed; then the rail from the rail mouth to the locking position is stretched toward the rail mouth by the amount of upsetting as the stretching amount, and after stretching, the rail is welded to the laid rail, and finally the rail from the rail mouth to the locking position is locked;

[0015] S9: At the tail of the dragon, stretch the rail toward the tail of the dragon and connect it to the existing rail after stretching; finally, lock the rail from the locking position to the tail of the dragon.

[0016] In this solution, the rail-changing vehicle is driven to change rails. The stretching amount of the rail is first determined based on the upsetting amount and the reserved rail gap, and then the stretching amount is used to calculate the unit rail section length L. The unit rail section length L is the distance from the dragon mouth to the locking position. The locking position is determined based on the distance and the rail is locked. After the position is locked, the rail is stretched toward the dragon mouth by a welding machine at the dragon mouth position to close the reserved gap. After stretching and closing, the rail is welded with the upsetting amount as the stretching amount; the rail-changing vehicle travels to the dragon tail position, and after the rail at the dragon tail falls into the rail bearing groove, the stretching machine is used to stretch the rail toward the dragon tail direction; in this seamless line laying method, the stretching amount is first determined, and then the rail is locked from the middle position, and stretched from the middle toward both ends of the dragon mouth and dragon tail. After the middle position of the rail is locked, it can be stretched toward the dragon mouth and dragon tail at the same time, which can greatly improve construction efficiency and save construction windows.

[0017] Furthermore, in S2, the return line is set up according to the two vertical and one horizontal operation standard, and the installation section of the return line is not less than 70mm 2 .

[0018] In this scheme, according to the two vertical and one horizontal operation standard, two return lines are set up along the track direction, and a return line is set up between two rails in the vertical track direction. The installation section of the return line is not less than 70mm 2 , to ensure that the current circuit is unobstructed. After the track-changing vehicle passes through the Longkou and Longwei sections, the return line will be switched in time to ensure uninterrupted return flow and prevent damage to electrical equipment.

[0019] Furthermore, S3 includes the following steps:

[0020] S301: Cut the existing rails, making a cut every 300-500 meters. If the rail gap at the cut is larger than 50mm, add a short rail head pad under the cut.

[0021] S302: Use splints to connect the cut edges of existing rails;

[0022] S303: Dismantle the sleeper fasteners in the track change section, reserving at least one fastener for every forty sleepers during dismantling.

[0023] In this solution, the existing rails need to be cut before the track is replaced. However, the cut rails still need to carry the rail-changing vehicle, so splints need to be used to connect the cuts, and some fasteners need to be reserved when removing the fasteners to ensure the stability of the existing rails and the safe operation of the rail-changing vehicle. In order to ensure the smooth operation of the rail-changing vehicle, a cut is made every 300-500 meters. In the actual construction section, the cutting distance can be appropriately shortened for the curved section.

[0024] Furthermore, S4 includes the following steps:

[0025] S401: The rail-changing vehicle moves to the rail-changing starting point and clamps the new rail and the old rail on the rail-hanging clamp of the rail-changing vehicle;

[0026] S402: Recording the temperature of the rail when it enters the rail groove;

[0027] S403: operating a rail-changing vehicle to replace the rails into the rail-supporting grooves, and removing the reserved fasteners when the rail-changing vehicle approaches the reserved fasteners;

[0028] S404: Record the temperature of the rail after it falls into the rail groove.

[0029] In this scheme, the rail temperature during operation is required to calculate the length of the unit rail section. In this scheme, the average temperature of the rail when it enters the rail groove and the temperature after the rail falls into the rail groove is used as the rail temperature during operation. The calculated length of the unit rail section is more accurate; when the rail changing car runs to the reserved fasteners, the fasteners are removed to ensure the safe operation of the rail changing car.

[0030] Furthermore, in S5, the stretching amount of the rail is calculated based on the upsetting amount of the welding machine and the reserved rail gap at the tappet:

[0031] Stretching amount Δl = upsetting amount + reserved rail gap

[0032] Here, Δl represents the stretch of the rail.

[0033] Furthermore, in S6, the rail length of the unit rail section is calculated based on the temperature of the rail when it enters the rail groove, the temperature of the rail after it falls into the rail groove, and the stretching amount:

[0034]

[0035] Among them, Δl represents the stretching of the rail, ΔT 入 Indicates the temperature of the rail when it enters the rail groove, ΔT 落 Indicates the temperature of the rail after it falls into the rail groove, T e It indicates the locking rail temperature, L is the length of the rail of the unit rail section, that is, the distance from the rail mouth to the locking position.

[0036] Furthermore, S7 includes the following steps:

[0037] S701: Determine the starting locking position at a position one rail length away from the longkou;

[0038] S702: Use fasteners to lock 40-50 meters from the starting locking position towards the dragon's tail.

[0039] In this solution, the length of the rail of a unit rail section is determined as the starting locking position, and the rail is locked for 40-50 meters from the locking position to ensure that the rail is firmly locked.

[0040] Furthermore, S8 includes the following steps:

[0041] S801: Support rollers under the rails, one every 10 meters;

[0042] S802: At the dragon mouth, use a welding machine to stretch and close the reserved rail seam;

[0043] S803: After closing, the rail from the spur to the locking position is stretched toward the spur using a welding machine with the upset amount as the stretching amount;

[0044] S804: welding the stretched rail to the laid rail;

[0045] S805: Use fasteners to lock the rails from the dragon mouth to the locking position section.

[0046] In this solution, the rail is stretched after the support roller is placed under the rail. The roller serves as a fulcrum to support the rail, so that the sliding friction between the bottom surface of the rail and the pad is converted into rolling friction between the bottom surface of the rail and the roller, thereby reducing the release resistance and alleviating the load of the stretching machine.

[0047] Furthermore, the upset amount in S804 is the average upset amount of the welding machine.

[0048] Furthermore, S9 includes the following steps:

[0049] S901: Support rollers under the rails, one every 10 meters;

[0050] S902: The rails are bumped at the tail of the dragon to release the internal stress of the rails; then a stretching machine is used to stretch the rails toward the tail of the dragon;

[0051] S903: After stretching, the rail is connected to the existing rail through a joint clamp;

[0052] S904: Adjust the position of the large rubber pad under the rail and lock the rail from the locking position to the tail section with fasteners. When locking, use an internal combustion bolt wrench to tighten the nut of the fastener.

[0053] In this solution, colliding the rails can release the stress inside the rails, making it easier for the rails to be laid without stress when stretched; after stretching the rails, they are connected to the existing rails and then locked to ensure that the rails remain in a stretched state when locked.

[0054] The beneficial effects of the present invention are:

[0055] In the seamless line laying method provided by the present invention, the stretching amount of the rail is first determined according to the average upsetting amount of the welding machine and the reserved rail seam of the rail, and then the stretching amount is deduced from the unit rail section rail length, and the rail is locked according to the unit rail section rail length. After locking, the rail can be stretched to both ends from the dragon mouth and the dragon tail position; different from the prior art in which the unit rail section rail length is first determined, and then the stretching amount of the rail is calculated based on the determined unit rail section rail length, after laying the rail of a unit rail section rail length, it is stretched at the dragon tail according to the calculated stretching amount, and when stretching the dragon tail, it is necessary to wait for the dragon mouth to be welded and locked 50 meters from the dragon mouth before stretching, which wastes the time waiting for the dragon mouth welding to be locked; so in this solution, after the middle position of the rail is locked, construction stretching in the dragon mouth and dragon tail directions can be carried out simultaneously, without wasting time waiting for the dragon head position to be welded and locked, which can greatly improve construction efficiency and save construction skylights.

[0056] In the seamless line laying method provided by the present invention, the stretching amount of the rail is first determined, and the length of the unit rail section is calculated based on the stretching amount. Therefore, when stretching at the dragon mouth or the dragon tail, it can be stretched into place at one time, and the construction efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a construction flow chart for a seamless line laying method using middle locking and two-end stretching;

[0058] Figure 2 This is a schematic diagram of the vehicle marshaling structure during seamless line laying. DETAILED DESCRIPTION

[0059] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0060] Example 1

[0061] This embodiment provides a seamless line laying method using middle locking and two-end stretching. The construction process of this method is as follows: Figure 1As shown, after the rail-changing vehicle has laid the new rails, the rail length of the unit rail section is calculated based on the upset amount and the reserved rail gap, and the rail is locked according to the unit rail section length. The rail is then stretched from the locked position toward the rail mouth and the rail tail, respectively. This solves the technical problem of the prior art of laying seamless lines, which wastes construction time and reduces construction progress during the construction process of stretching and locking the rail tail after the rail mouth is welded and locked.

[0062] Specifically include:

[0063] S1: Set up signal protection; issue a construction blockade order and start work, which specifically includes:

[0064] Set up signal protection: Set up mobile stop signal protection on the main line of the seamless line laying section, and set up mobile deceleration signal protection on the adjacent line.

[0065] S2: Overlapping the return line at the starting and ending points of the track change section, which specifically includes:

[0066] According to the two vertical and one horizontal operation standard, two return lines are set up along the track direction, and a return line is set up between two rails in the vertical track direction. The installation section of the return line is not less than 70mm 2 .

[0067] S3: Cutting the existing rails and removing the sleeper fasteners of the existing rails in the rail replacement section, which specifically includes:

[0068] S301: Cut the existing rails, making a cut every 300-500 meters. If the rail gap at the cut is larger than 50mm, add a short rail head pad under the cut.

[0069] S302: Use splints to connect the cut edges of existing rails;

[0070] S303: Remove the sleeper fasteners in the track-changing section, and reserve at least one fastener for every forty sleepers during the removal process to ensure that the track-changing vehicle can travel safely and stably.

[0071] S4: The rail-changing vehicle changes rails and collects and records the temperature ΔT when the rail enters the rail groove. 入 and the temperature ΔT of the rail after it falls into the rail groove 落 , which specifically include:

[0072] S401: The rail-changing vehicle runs to the rail-changing starting point, clamps the new rail and the old rail on the rail-hanging clamp of the rail-changing vehicle, and switches the return line to the new rail;

[0073] S402: Measure and record the temperature ΔT of the rail when it enters the rail groove 入 , the temperature measurement position is on the dark side of the rail waist;

[0074] S403: operating a rail-changing vehicle to replace the rails into the rail-supporting grooves, and removing the reserved fasteners when the rail-changing vehicle approaches the reserved fasteners;

[0075] S404: Measure and record the temperature ΔT of the rail after it falls into the rail groove 落 The temperature measurement position is on the dark side of the rail waist.

[0076] S5: The rail-changing vehicle moves to the gantry. After the rail at the gantry falls into the rail groove, the stretching of the rail is calculated based on the welding machine's upsetting amount and the reserved rail gap at the gantry:

[0077] Stretching amount Δl = upsetting amount + reserved rail gap

[0078] Here, Δl represents the stretch of the rail.

[0079] S6: According to the temperature ΔT when the rail enters the rail groove 入 , the temperature ΔT of the rail after it falls into the rail groove 落 And the stretching amount Δl is used to calculate the rail length of the unit rail section:

[0080]

[0081] Among them, Δl represents the stretching of the rail, ΔT 入 Indicates the temperature of the rail when it enters the rail groove, ΔT 落 Indicates the temperature of the rail after it falls into the rail groove, T e It indicates the locking rail temperature, L is the length of the rail of the unit rail section, that is, the distance from the rail mouth to the locking position.

[0082] S7: Rail position locking, which specifically includes:

[0083] S701: Determine the starting locking position at a position of a rail length L from the longkou;

[0084] S702: Use fasteners to lock from the starting locking position toward the dragon's tail.

[0085] S8: At the spur line, the reserved rail gap is stretched and closed; the rail from the spur line to the locking position is stretched toward the spur line by the upset amount as the stretching amount; after stretching, the rail is welded to the laid rail; and finally, the rail from the spur line to the locking position is locked. The steps include:

[0086] S801: Support rollers under the rails, one every 10 meters;

[0087] S802: At the dragon mouth, use a welding machine to stretch and close the reserved rail seam;

[0088] S803: After closing, the rail from the cam to the locking position is stretched toward the cam using a welding machine with the upset amount as the stretching amount;

[0089] S804: welding the stretched rail to the laid rail, with the upsetting amount during welding being the average upsetting amount of the welding machine;

[0090] S805: Use fasteners to lock the rails from the dragon mouth to the locking position section.

[0091] S9: At the tail of the dragon, the rail is stretched toward the tail of the dragon and connected to the existing rail after stretching; finally, the rail from the locking position to the tail of the dragon is locked; specifically, it includes:

[0092] S901: Support rollers under the rails, one every 10 meters;

[0093] S902: The rails are bumped at the tail of the dragon to release the internal stress of the rails; then a stretching machine is used to stretch the rails toward the tail of the dragon;

[0094] S903: After stretching, the rail is connected to the existing rail through a joint clamp;

[0095] S904: Adjust the position of the large rubber pad under the rail and lock the rail from the locking position to the tail section with fasteners. When locking, use an internal combustion bolt wrench to tighten the nut of the fastener.

[0096] After the laying is completed, the rail collection vehicle is used to recycle the short rail section. The oxygen cutting personnel cut and dismantle the old rails, lay them down on the ballast shoulder, and wait for recycling. After the construction is completed, the rail replacement vehicle is assembled and leaves. The assembly order is: rail vehicle + front flash welding + normalizing + rail replacement vehicle + rear gas pressure welding + rail vehicle. Figure 2 As shown. According to actual usage, flatbed cars, rail collecting cars, etc. can be added to the group and the grouping order can be adjusted.

[0097] Before the seamless track laying operation, it also includes:

[0098] Rail transportation: using long rail transport vehicles to transport rails to the CWR laying section;

[0099] Unloading rails: unloading rails from long rail transport vehicles, with the unloading direction being the same as the construction direction;

[0100] Rail welding: use mobile rail welding vehicle to weld rails and normalize the rail welds.

[0101] In this embodiment, after the existing rails are cut, the cuts are connected with splints. When removing the sleeper fasteners in the rail-changing section, at least one fastener is reserved for every forty sleepers. The cut rails will also support the rail-changing vehicle, so splints are required to connect the cuts to ensure an uninterrupted connection. To ensure the stability of the existing rails, some fasteners are reserved when removing the fasteners, ensuring the safe operation of the rail-changing vehicle.

[0102] In this embodiment, when cutting existing rails, a cut is made every 300-500 meters. If the rail gap at the cut is greater than 50mm, a short rail head is added. If the cut section is too short, the rail-changing vehicle will need to frequently change the existing track during operation, reducing construction efficiency. If the cut section is too long, the rail stability will be affected, making it impossible to ensure smooth operation of the rail-changing vehicle. Therefore, cutting every 300-500 meters is most appropriate. In actual construction sections, the cutting distance can be appropriately shortened for curved sections.

[0103] In this embodiment, the rail temperature during operation is required to calculate the length L of the rail of the unit rail section. In this solution, the temperature ΔT when the rail enters the rail groove is used. 入 and the temperature ΔT of the rail after it falls into the rail groove 落 The average value of is used as the rail temperature during operation, and the calculated unit rail section rail length L is more accurate; when the rail-changing vehicle runs to the reserved fasteners, the fasteners are removed to ensure the safe operation of the rail-changing vehicle.

[0104] In this embodiment, when the rail-changing vehicle passes the dragon's mouth and tail, the return line must be switched to the newly laid rails in time to ensure uninterrupted return flow and prevent electrical equipment from being burned out.

[0105] In this embodiment, the rail-changing vehicle is the HGCZ-2000. This new generation of seamless rail replacement vehicles, developed in China, boasts high speed and efficient rail-changing capabilities. Its combination of a center-locked rail and end-stretching construction method significantly improves construction efficiency and reduces construction time constraints. The rail welding vehicle is the YHGQ-1200 self-propelled pneumatic rail welding vehicle.

[0106] Example 2

[0107] Based on Example 1, this embodiment provides a seamless track laying method using middle locking and two-end stretching, and performs seamless track laying on the Haoji Line from Hejin West to Hancheng North K493+370 to K492+670 railway section, with track replacement at 700 meters during the laying process.

[0108] Specifically include:

[0109] S1: Set up signal protection; issue a construction blockade order and start work;

[0110] S2: Overlap the return line at the starting and ending points of the track change section;

[0111] S3: Cut the existing rails and remove the sleeper fasteners of the existing rails in the rail replacement section;

[0112] S4: Use the HGCZ-2000 rail-changing vehicle to lay the new rail into the rail groove; collect and record the temperature ΔT of the rail when it enters the rail groove. 入 and the temperature ΔT of the rail after it falls into the rail groove 落 ; Measure the temperature ΔT when the rail enters the rail groove 入 The temperature of the rail after it falls into the rail groove is 18℃. 落 is 18℃;

[0113] S5: The rail-changing vehicle moves to the cam, and after the rail at the cam falls into the rail groove, the rail stretching Δl is calculated based on the welding machine's upsetting amount and the reserved rail gap at the cam.

[0114] Stretching amount Δl = upsetting amount + reserved rail gap

[0115] The average upset amount of the welding machine is used as the upset amount, and the average upset amount is 35mm; the reserved rail gap of the dragon mouth is 10mm; the total stretching amount Δl is 45mm;

[0116] S6: According to the temperature ΔT when the rail enters the rail groove 入 , the temperature ΔT of the rail after it falls into the rail groove 落 And the stretching amount Δl calculate the unit rail length L:

[0117]

[0118] Construction day T e The temperature is 29°C, and the calculated rail length L of the unit rail section is 347 meters;

[0119] S7: The rail position is locked, starting from 347 meters from the dragon mouth and locked 50 meters towards the dragon tail;

[0120] S8: At the rail mouth, use a welding machine to stretch and close the reserved rail gap by 10mm, and use the welding machine to stretch the rail toward the rail mouth with the amount of upsetting as the stretching amount. After stretching, weld the rail to the laid rail, and finally use fasteners to lock the rail from the rail mouth to the locking position;

[0121] S9: At the tail of the dragon, a stretching machine is used to stretch the remaining 353 meters of rails toward the tail of the dragon. After stretching, they are connected to the existing rails through splints. Finally, fasteners are used to lock the rails from the locking position to the tail of the dragon.

[0122] Those skilled in the art will appreciate that the embodiments herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the invention.

Claims

1. A seamless line laying method using middle locking and two-end stretching, characterized in that: The following steps are involved: S1: Set up signal protection; issue a construction blockade order and start work; S2: Overlap the return line at the starting and ending points of the track change section; S3: Cut the existing rails; remove the sleeper fasteners of the existing rails in the rail replacement section; S4: The rail-changing vehicle operates to change rails, and collects and records the temperature of the rails when they enter the rail-supporting groove and the temperature of the rails after they fall into the rail-supporting groove; S5: The rail-changing vehicle runs to the dragon mouth. After the rail at the dragon mouth falls into the rail-supporting groove, the stretching amount of the rail is calculated according to the upsetting amount of the welding machine and the reserved rail gap at the dragon mouth: Stretch = Upsetting amount + reserved rail gap in, Indicates the stretch of the rail; S6: Calculate the length of the rail of the unit rail section according to the temperature of the rail when entering the rail groove, the temperature of the rail after falling into the rail groove, and the stretching amount, that is, obtain the distance between the gantry and the locking position: in, Indicates the stretch of the rail, Indicates the temperature of the rail when it enters the rail groove. Indicates the temperature of the rail after it falls into the rail groove. Indicates locked rail temperature. L The length of the rail of the unit rail section is the distance from the rail mouth to the locking position; S7: Locking the rail position; locking from the length of the rail of the unit rail section away from the dragon mouth toward the dragon tail; S8: At the cam, the reserved rail gap is stretched and closed; the rail from the cam to the locking position is stretched toward the cam by using the upset amount as the stretching amount; after stretching, the rail is welded to the laid rail; and finally, the rail from the cam to the locking position is locked; The S8 comprises the following steps: S801: Support rollers under the rails, with one roller supporting the rails every 10 meters. S802: Using a welding machine to stretch and close the reserved rail seam at the dragon mouth; S803: After closing, the rail is stretched from the rail mouth to the locking position toward the rail mouth by using a welding machine with the upset amount as the stretching amount; S804: welding the stretched steel rail to the laid steel rail; S805: Locking the rail from the dragon mouth to the locking position section using a fastener; S9: At the tail of the dragon, stretch the rail toward the tail of the dragon, and connect it to the existing rail after stretching; finally, lock the rail from the locking position to the tail of the dragon; The S9 comprises the following steps: S901: Support rollers under the rails, with one roller supported every 10 meters; S902: performing a rail collision on the rail at the tail of the dragon to release the internal stress of the rail; and then using a stretching machine to stretch the rail toward the tail of the dragon; S903: After stretching, the steel rail is connected to the existing steel rail via a joint clamp; S904: Adjust the position of the large rubber pad under the rail, and lock the rail from the locking position to the dragon tail section using a fastener. When locking, use an internal combustion bolt wrench to tighten the nut of the fastener.

2. The seamless track laying method with middle locking and two-end stretching according to claim 1 is characterized in that: In S2, the return line is set up according to the two vertical and one horizontal operation standard, and the installation section of the return line is not less than 70mm 2 .

3. The seamless line laying method with middle locking and two-end stretching according to claim 1 is characterized in that: The S3 includes the following steps: S301: cutting the existing rails, cutting a cut every 300-500 meters, and adding a short rail head under the cut if the rail gap at the cut is larger than 50 mm; S302: Connecting the cut edges of the existing rails with splints; S303: Dismantle the sleeper fasteners in the track change section, reserving at least one fastener for every forty sleepers during dismantling.

4. The seamless line laying method with middle locking and two-end stretching according to claim 3 is characterized in that: The S4 comprises the following steps: S401: The rail-changing vehicle moves to the rail-changing starting point and clamps the new rail and the old rail on the rail-hanging clamp of the rail-changing vehicle; S402: Recording the temperature of the rail when it enters the rail groove; S403: operating the rail-changing vehicle to replace the rail into the rail-supporting groove, and removing the reserved fastener when the rail-changing vehicle approaches the reserved fastener; S404: Recording the temperature of the rail after it falls into the rail-bearing groove.

5. The seamless track laying method with middle locking and two-end stretching according to claim 1 is characterized in that: The S7 comprises the following steps: S701: Determine the starting locking position at a position one rail length away from the dragon mouth; S702: Use fasteners to lock 40-50 meters from the starting locking position toward the dragon's tail.

6. The seamless track laying method with middle locking and two-end stretching according to claim 1 is characterized in that: The upset amount in S803 is the average upset amount of the welding machine.

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