Urban rail transit ballast track bed construction method based on shock pads

Abstract

The invention discloses an urban rail transit ballast track bed construction method based on a shock pad. The urban rail transit ballast track bed construction method comprises the following steps that S1, construction preparation is conducted; s2, surveying and lofting: lofting a line central control point by taking a track CP III basic control network as a reference, and lofting an eccentric control point by taking an outer offset distance L of the line central control point; s3, pouring and maintenance of a base cushion layer; s4, anti-vibration pad laying; s5, paving a track bed line; and S6, track lifting and repairing. The ballast track bed has the beneficial effects that the shock pad is additionally arranged on the base cushion layer, so that the structure of the ballast track bed is improved, a good shock absorption effect is achieved, and the overhaul period of a line is delayed; a line center control point and an eccentric control point are arranged, ballast bed construction with the damping function is achieved, meanwhile, after pouring is completed, an outer deviation side line serves as a track laying datum, a cushion layer is poured through the line center control point, track laying is controlled through the eccentric control point, and the construction operation efficiency is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of ballasted track bed construction, in particular to a construction method of a ballasted track bed for urban rail transit based on a shock-absorbing pad. Background Art

[0002] Ballasted track refers to a track with a stone granular ballast bed as the foundation under the track, which is also commonly known as a gravel ballast track. It is one of the forms of track structure. The ballast bed is an important part of the track and the foundation of the track frame. The ballast bed usually refers to the stone ballast (ballast) cushion layer laid on the roadbed surface under the railway sleepers. Its main function is to support the sleepers, evenly transfer the huge pressure on the top of the sleepers to the roadbed surface, and fix the position of the sleepers to prevent the sleepers from moving longitudinally or laterally, greatly reducing the deformation of the roadbed while also alleviating the impact of the locomotive wheels on the rails.

[0003] Most of the existing ballasted trackbeds are constructed using the track laying method, which has low operating efficiency and requires multiple track shifting to align with the center line of the line. In some densely built cities, the noise during construction in the track area is relatively loud, and the working environment is poor. The vibration and secondary structural noise generated by the train operation have caused obvious interference to residents and buildings around the line. At the same time, due to the significant increase in train speeds, the existing ballasted trackbeds basically have no shock-absorbing function, and their overhaul cycle is relatively frequent. Therefore, a ballasted trackbed construction process with shock-absorbing function is urgently needed. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for constructing a ballasted track bed for urban rail transit based on shock-absorbing pads, which can realize the construction of a ballasted track bed with a shock-absorbing function, increase the shock-absorbing performance of the ballasted track bed, reduce noise, and at the same time delay the overhaul period of the line and improve the construction efficiency.

[0005] The objective of the present invention is achieved through the following technical solution: A construction method for urban rail transit ballasted track bed based on shock-absorbing pads, comprising the following steps: S1. Construction preparation: Check the construction site to ensure that the construction site meets the construction conditions. The inspection of the construction site includes the inspection of the roadbed density and the roadbed surface flatness. The roadbed density meets the roadbed subgrade surface compaction coefficient of not less than 0.93, the roadbed subgrade bottom layer compaction coefficient of not less than 0.91, and the roadbed surface flatness meets the surface flatness deviation of ±50mm; Before construction begins, on-site construction technicians will investigate the construction site to confirm whether there is water leakage, silt, garbage, etc. within the construction site. After the above conditions are confirmed, the roadbed will be handed over together with the owner, supervisor and the civil construction unit of the parking lot line, and the density and surface flatness of the handed-over roadbed will be inspected and accepted. The construction site should have a good drainage system to ensure that the strength and compaction of the roadbed bed are not affected by rainwater and mud will not occur.

[0006] S2. Surveying and staking out: Taking the track CPⅢ basic control network as the reference, the center control point (pile point) of the line is staked out, and the eccentric control point (pile point) is staked out with the outer deviation distance L of the center control point of the line. The line connecting the center control points of the line is the center line of the line, and the line connecting the eccentric control points is the outer side line; S3, pouring and curing of the base cushion layer, including the following sub-steps: (1), cleaning the area within the construction site; (2), after the cleaning is completed, with the line centerline as the center and the outer side line as the boundary, tie the steel bars of the base cushion layer on the roadbed, and the steel bars are at least two layers; (3), after the steel bars are tied, install the base cushion layer formwork; (4), after the base cushion layer formwork is installed, pour concrete in the formwork; (5), after the concrete pouring is completed, the base cushion layer is formed, and the base cushion layer is cured until its concrete strength reaches 5MPa or more, and the base cushion layer formwork is removed, and the side of the base cushion layer coincides with the outer side line; (6), continue to cure the base cushion layer until its concrete strength is not less than 75% of the design strength, and then proceed to the next step. The total curing time of the base cushion layer is not less than 7 days; S4. Laying of vibration damping pads: Lay vibration damping pads on the base cushion layer in a shrinking manner. After the vibration damping pads are laid in place, they are fixed on the base cushion layer. The side edge line outside the place where the vibration damping pads are laid is used as the standard for being in place. Shrinking means that the vibration damping pads are laid in a manner of reducing their width. The distance between the side edge of the vibration damping pad and the side edge of the base cushion layer is 200-400mm. The vibration damping pads are laid in sections, and the adjacent vibration damping pads are overlapped at the ends. The overlap width is 20-50mm.

[0007] S5. Track bed laying: ballast, sleepers and rails are laid on the base cushion layer in sequence. The sleepers are positioned based on the outer side line, rail joints are reserved, and then fasteners are installed. When laying rails, the staggered amount of rail joints is not more than 40mm; Among them, the reserved rail gap is one of the important indicators for track engineering quality control. It is ensured that the reserved rail gap meets the requirements of the locked track. Under the constraints of the joint resistance and the ballast bed resistance, the rail has enough expansion and contraction space to release some temperature stress. When the rail temperature reaches the highest temperature in history, the rail gap is closed and the rail end is not tightly stressed. When the rail temperature drops to the lowest, the rail gap does not exceed the maximum structural rail gap, which meets the basic requirements of ordinary line tracks for the rail joint structure.

[0008] According to the track design standards and the highest and lowest track temperatures in the local history, and in accordance with the provisions of TB10302-96 "Railway Construction and Acceptance Specifications", the reserved rail gap is calculated using the α=0.0118 (Tmax-t) LC formula. When actually reserving the track gap, it is slightly increased according to the degree of center deviation and smoothness of the rail row during track laying, and the increase value does not exceed 2mm. On the day of track laying, each section is inspected, and the total deviation of the inspection results is recorded in the engineering log, and adjusted and eliminated when laying the track the next day.

[0009] During the track leveling operation, a hydraulic track leveler is used to level the track gap according to the specified track gap value. After the track maintenance meets the standards, the track gap quality inspection is carried out. The track gap quality inspection is in accordance with the provisions of the "Railway Construction and Acceptance Specifications", based on the track gap inspection value, and is inspected in sections. The length of each section is not more than 1km. The actual track gap average value in each inspection section is based on the track gap inspection value. The allowable deviation is not more than ±2mm, and it is avoided to have more than 3 consecutive blind gaps or exceed the maximum structural track gap. There is an on-duty engineer at the track laying site. During the track laying operation, the track temperature is measured every 2 hours, and the reserved track gap is calculated and adjusted accordingly. The track gap is reserved using rail gap pieces to ensure that the reserved track gap of the newly laid track row is correct and meets the theoretical requirements. After the track rows are connected, the newly laid track rows should be immediately aligned and adjusted, with a deviation of no more than 2 cm from the center line, to reduce the impact of track alignment on the accuracy of the reserved track gap. After track laying, the joint bolts and sleeper fasteners should be immediately supplemented, the rail gap pieces should be removed, and within 3 days after track laying, the joint bolts should be retightened once a day according to the specified torque to ensure the joint resistance of the rails and control the reserved track gap.

[0010] The reserved track joints of the newly laid tracks are inspected section by section when laying the tracks on the same day, and the total deviation of the inspection results is recorded in the engineering log, and adjusted and eliminated when laying the tracks the next day. A hydraulic track leveler is used during the whole track operation to level the track joints according to the specified track joint value. After the road maintenance meets the standards, the track joint quality inspection is carried out. The track joint quality inspection is carried out in sections according to the "Railway Track Construction Acceptance Specifications". The section length is not more than 1km. The actual track joint average value in each inspection section is based on the track joint inspection value. The allowable deviation is not more than ±2mm. Before laying the tracks, the piles in the roadbed are investigated, and the placement position of the sleepers is marked on the waist of the rail to strictly control the spacing between the sleepers. Before laying the tracks, the track matching operation is carried out to ensure that the misalignment of the rail joints is not more than 40mm. At the same time, the appearance quality of the rails is checked to ensure that there are no hard bends or defects. If necessary, a straight rail is used to straighten them. During the track lifting operation, the track lifting height meets the requirements of the specifications each time.

[0011] Among them, the rail joint reservation shall comply with the provisions of the "Railway Track Construction and Acceptance Specifications". When the rail temperature is lower than the highest rail temperature in the local history, there shall be no more than three consecutive blind joints. Under no circumstances shall there be structural rail joints. The difference between the actual average value of the rail joint and the calculated average value is ±2mm; the joint misalignment is ≯1mm; the joint misalignment linear value is ≯40; the track gauge error is allowed to be +3mm, -2mm; the difference between the track center and the designed center line is ≯20mm.

[0012] S6. Track lifting and repair: After the rails are laid, the trackbed components are repaired and the trackbed surface is tamped to make the cross section of the trackbed meet the design requirements, and all kinds of fasteners are installed and positioned correctly. The track is straight in the long-distance direction, without hard bends, smooth curves, no reverse bends or goose heads, no reverse superelevation and triangular pits, and the upper and lower edges of the trackbed slope are neat and parallel to the rails, and the trackbed construction is completed.

[0013] The outer deviation distance L is 1 / 2 of the designed width of the base cushion layer.

[0014] The shock-absorbing pads in this scheme use rubber shock-absorbing pads. This type of product has the characteristics of low natural frequency, good vibration reduction effect, fast laying speed, and long service life. Specifically, the USM series of products can be used. The USM series of products are designed in a "sandwich structure + cone truncated type" way, so that the load and deformation curves show typical nonlinear characteristics, and a stable natural frequency can be obtained after a certain preload. The shock-absorbing pad is fixed on the base cushion layer, that is, a rubber shock-absorbing pad ballasted track bed is formed, which innovates the super-large cover project of urban rail transit and changes the structural form of the existing ballasted track bed. The rubber shock-absorbing pad is laid on the lower part of the track bed in the form of surface support or strip support, providing isolation and elasticity between the track and the lower structure, reducing the transmission of wheel-rail vibration to the lower foundation, and is mainly used to reduce the interference of vibration and secondary structural noise generated by train operation on residents or buildings around the line, or protect the building structure from vibration damage. At the same time, the rubber shock-absorbing pad ballasted track bed can also improve the force characteristics of the ballast and delay the overhaul cycle of the line.

[0015] The applicant changed the structure of the existing ballasted track bed and added rubber vibration damping pads (laid on the lower part of the track bed in the form of surface support or strip support), so the construction method should also be adjusted. However, in actual construction, after the base cushion layer is poured, the center line of the line needs to be re-measured and re-positioned, and the process is relatively cumbersome. Therefore, in this scheme, the center control point and eccentric control point of the line are staked out before pouring, and the center control point of the line is used to control the pouring of the cushion layer, and then the eccentric control point is used to control the track laying. Compared with the existing ballasted track bed track laying method, the vibration damping pad laying construction technology has greatly improved the construction efficiency, the track bed laying quality is guaranteed, and the noise of driving operations in the track area is greatly reduced. It meets the national industrial development requirements. At the same time, after the base cushion layer is poured, the eccentric control point (outer side line) is used as the reference, bidirectional operation can be achieved, and construction from both sides to the center can be achieved, which greatly improves the operation efficiency.

[0016] The beneficial effects of the present invention are as follows: (1) a shock-absorbing pad is added to the base cushion layer, which improves the structure of the ballasted track bed and achieves a better shock-absorbing effect. Isolation and elasticity are provided between the track and the lower structure, and the transmission of wheel-rail vibration to the lower foundation is reduced. It is mainly used to reduce the interference of vibration and secondary structural noise generated by train operation on residents or buildings around the line, and delay the overhaul period of the line; (2) during construction, a line center control point and an eccentric control point are set, which changes the existing ballasted track bed construction process and realizes the track bed construction with shock-absorbing function. At the same time, after the pouring is completed, the outer side line is used as the track laying reference, the line center control point is used to pour the cushion layer, and the eccentric control point is used to control the track laying, which greatly improves the construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a construction flow chart of the present invention; Figure 2 is a cross-sectional view of the ballasted track bed of the present invention; Figure 3 It is a schematic diagram of the installation of the shock-absorbing pad of the present invention.

[0018] In the figure, 1-rail, 2-sleeper, 3-base ballast, 4-shock-absorbing pad, 5-base cushion layer, 6-rebar. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0020] like Figure 1As shown, the construction method of urban rail transit ballasted track bed based on shock-absorbing pads includes the following steps: S1. Construction preparation: Inspect the construction site to ensure that it meets the construction conditions. The inspection of the construction site includes the inspection of the roadbed density and the flatness of the roadbed surface.

[0021] The compaction coefficient of the roadbed surface layer is not less than 0.93, and the compaction coefficient of the roadbed bottom layer is not less than 0.91. The surface flatness of the roadbed surface is not less than ±50 mm.

[0022] S2. Measurement and setting out: Figure 2 As shown, the track CPⅢ basic control network is used as a reference to lay out the line center control point, and the eccentric control point is laid out with the outer deviation distance L of the line center control point. The line connecting the line center control points is the line center line, and the line connecting the eccentric control points is the outer side line. The outer deviation distance L is 1 / 2 of the design width of the base cushion layer, wherein the line center line is a, the outer side line is c, and the outer edge line of the shock-absorbing pad is b. The position of the shock-absorbing pad 4 is determined by maintaining the distance between the b and c lines to determine whether the shock-absorbing pad is installed in place. The line center control point (i.e., the layout of the a and c lines) is used to control the pouring of the base cushion layer, and the eccentric control point (i.e., the layout of the c line) is used to control the track laying. S3, pouring and curing of the base cushion layer, including the following sub-steps: (1), cleaning the area within the construction site; (2), after cleaning, with the line centerline as the center and the outer side line as the boundary, tie the steel bars 6 of the base cushion layer 5 on the roadbed. The steel bars 6 of the base cushion layer 5 are constructed by the scheme of "base processing and on-site tying". After the processing of the track laying base, the base cushion layer steel bars are transported from the base to the construction site by the base truck crane. The tying of the steel bars 5 is strictly in accordance with the design drawings. The steel bars 6 are HRB400 with a diameter of 10. The spacing between the longitudinal and transverse steel bars is 200mm. Each transverse steel bar is divided into two upper and lower bars with the same length, namely the top and bottom steel bars; (3), after the steel bars are tied, the base cushion layer template is installed. The expansion joint needs to be set on the base cushion layer template according to the length position of the design drawing. The steel bars at the expansion joint position need to be disconnected, and the expansion joint template is installed. The template is erected to detect the structural height according to the base mark, determine the template specifications, clean the template surface and apply the release agent. The templates shall be erected in accordance with the design requirements to ensure that they are straight, tight and leak-proof. The template support shall be inspected and accepted to ensure that they meet the design and specification requirements. The deformation joints and ditch templates of the integral track bed concrete shall be erected straight and firm, with the allowable deviations of: position ±5mm; verticality 2mm; (4) After the base cushion template is installed, concrete is poured in the template. The top surface elevation of the base cushion is calculated based on the design elevation of the rail top surface. The surface position of the base cushion is marked on the base elevation control wire reference line with tape as the control line for concrete pouring construction. The base elevation and surface flatness shall be strictly controlled during construction. The base cushion is cast on-site with C35 concrete. During pouring, the height of the discharge port shall be minimized to reduce the impact of concrete on the steel bars. An inserted high-frequency vibrator shall be used for vibration. During the concrete vibration process, repeated vibration shall be avoided to prevent over-vibration. The vibrator shall be inserted vertically into the concrete. The vibrator shall be inserted quickly and pulled out slowly to avoid voids. The concrete vibration time should be appropriate. When the concrete stops sinking, bubbles, slurry, and the surface is flat, stop vibrating at that point and move to the next point. During vibration, the stability of the formwork support and the tightness of the joints should be checked to prevent leakage and mold running during the concrete vibration process. Concrete pouring must not be interrupted. Each single slab must be poured in one go to prevent backfilling and secondary pouring. The temperature of the concrete entering the mold should be controlled between 5-25℃. When the ambient temperature is greater than 30℃, cooling measures should be taken. When the concrete is finished, the elevation should be strictly controlled according to the design. The flatness requirement is 5mm, and the elevation error of the base top surface should be controlled within +0, -10mm. The allowable deviation of the base width is ±10mm; (5) After the concrete is poured, a base cushion layer is formed. When the concrete is initially set, it is watered and cured by using geotextiles and covered with curing cotton. The plastic film is pressed and sealed around to prevent moisture from escaping too quickly.According to the external environment temperature, the number of times of watering per day is mainly to ensure that the concrete surface is moist. The total time of base cushion curing is not less than 7 days. The base cushion curing is carried out until its concrete strength reaches 5MPa or above, the base cushion formwork is removed, and the side of the base cushion coincides with the outer side line; (6) Continue to cure the base cushion until its concrete strength is not less than 75% of the design strength, and then proceed to the next step;. S4, laying of vibration-damping pads: laying vibration-damping pads 4 on the base cushion layer 5 in a shrinking manner, fixing the vibration-damping pads 4 on the base cushion layer 5 after they are laid in place, and the side edge line of the vibration-damping pads 5 outside the laying in place is used as the in-place reference; S5, track bed laying: ballast 3, sleepers 2 and rails 1 are laid on the base cushion layer in sequence, wherein the position of the sleepers 2 is positioned based on the outer side line, rail seams are reserved for the rails 1, and then fasteners are installed; S6. Track lifting and repair: After the rail 1 is laid, the various components of the ballast bed are repaired and the ballast bed surface is tamped to make the cross-section of the ballast bed meet the design requirements, and the upper and lower edges of the ballast bed slope are neat and parallel to the rail 1, completing the ballast bed construction.

[0023] Shrinking means that the vibration damping pad is laid in a manner of reducing its width, and the distance between the side edge of the vibration damping pad and the side edge of the base cushion layer is 200-400mm. Figure 3 As shown, the shock-absorbing pads are laid in sections, and the adjacent shock-absorbing pads are overlapped at the ends. The overlap width T is 20-50 mm.

[0024] In step S5, the staggered amount of rail joints during rail laying is no more than 40 mm.

[0025] As a further improvement of this solution, a re-measurement and verification step is provided between step S1 and step S2, specifically including: (1) surveying and setting the cushion base points and the track laying encryption base points The pad and track laying densification benchmarks are set up according to 10m for straight lines and 5m for curves. During surveying and setting, the total station is set up on the center line of the line, and a total of 4 pairs (at least 3 pairs) of CPⅢ points are measured for rear intersection with each other symmetrically in front and back. After the free station setting accuracy meets the requirements (dx=0.7mm, dy=0.7mm, dh=0.7mm, orientation error 1.5″), the station setting is completed. After the station setting, the coordinate residual of the CPⅢ point does not exceed 2mm. Then the polar coordinate method is used to carry out construction layout and record elevation information, and then drill holes to bury the standard benchmark. After burying the standard benchmark, precise data collection begins. The CPⅢ points and the densification benchmarks of the same survey station are observed using the left panel of the total station, and multiple half-round observations are carried out. The order of data collection is: A. Observe the CPⅢ points in sequence; B. Use a precision prism group to Collect each encrypted pile in turn from far to near; C. Carry out the second half of the survey according to the first two items, and finally observe CPⅢ 4 times and the encrypted pile 3 times. The observation distance of each station is about 60m (about 10-12 observation piles), and the shortest measurement distance is greater than 5m. Repeat observation of no less than 2 pairs of CPⅢ points between stations, and re-observe 3 to 5 encrypted base marks of the previous station. The above observation data, after adjustment, reaches the following accuracy: the relative accuracy of the plane of adjacent points is not more than 0.2mm; the difference between the coordinate value of each half of the survey and its average value of the encrypted base mark is ≤0.4mm; the allowable deviation of the plane position of the encrypted base mark: ≤0.3mm horizontally, ≤0.4mm vertically; after the adjustment calculation, calculate the correction number of each encrypted base mark to the center line of the line, so that the deviation of the corrected encrypted base mark from the center line position reaches 0.5mm.

[0026] (2) Elevation re-measurement The elevation measurement is carried out using a high-precision electronic level and a matching indium steel ruler (only one is used). The measurement is carried out by combining the leveling method with the mid-view leveling method. The dense piles are used as the mid-view points. Except for the first and last CPⅢ points, the remaining CPⅢ points are used as the turning points of the leveling line. The leveling line adopts the "single line, round-trip measurement" mode. The length of a measurement section is preferably 300m, and 3-5 dense base marks should be overlapped between the measurement sections. The difference between the round-trip measurement elevation value of the dense base mark point and its average value is not greater than 0.3mm; the difference in the elevation of the dense piles in the overlapping area is not greater than 0.3mm; the relative accuracy of the elevation between adjacent track benchmarks is not greater than 0.1mm; according to the difference between the calculated base mark top elevation and the design, make another measurement after adjustment to verify whether it meets the standard accuracy requirements.

[0027] Through re-measurement and verification, strict control was carried out on both plane position and elevation control to ensure construction conditions.

[0028] The shock-absorbing pads can be of two types: USM-1000W and USM-2030. USM-2030 is a transitional shock-absorbing pad that is laid about 20-30m before the boundary of the roadbed type. The shock-absorbing pad is laid 250mm away from the edge of the cushion layer. The shock-absorbing pad is cut and laid according to the requirements and fixed. When fixed, the overlap is reinforced with air nails, and each shock-absorbing pad is anchored with two pairs of spikes. Geotextile is used to seal the edges of the shock-absorbing pads and air nails are used to reinforce them.

[0029] When laying the line, the existing roads will be used to unload the ballast, rails, sleepers and fasteners near the construction section. First, the ballast will be laid on the connected roadbed, and the sleepers will be hoisted to the construction site by a truck crane, and the sleepers will be anchored with spiral spikes. The rails will be transported in pairs and placed in the sleeper bearing grooves. The fasteners will be dispersed and the line will be assembled in sections. The assembled track line will be repeatedly raised and maintained using a track lifter, a track shifter and a small tamping machine to finally meet the line standard requirements.

[0030] The ballast is transported to the construction site by car, and the existing machinery and manual ballast laying and leveling are used. The thickness of the ballast of this section of crushed stone roadbed is not less than 250mm, and a single-layer ballast roadbed is used. The top width of the roadbed is not less than 2.9m, the ballast shoulder width is 200mm, and the slope rate is 1:1.5. The outer side of the roadbed is widened by 100mm in the curved section with a radius R≤300m. The ballast surface is 20mm lower than the sleeper. The top surface of the ballast should be flat, and the elevation deviation is allowed to be ±20mm.

[0031] The sleepers are laid with new II concrete sleepers at a rate of 1440 km / sleeper. The sleepers must be square in curves and straight sections to ensure that there are no missing pieces or corners. Since the center point of the line disappears after pouring, this plan uses the eccentric control point as the basis for laying the sleepers.

[0032] The rails are transported to the laying site by forklifts, and the rails are spread on the sleepers according to the laying order of the rail section table by manual cooperation. Then, according to the design standards and the requirements of the fastener assembly drawing, the track connection accessories are placed at both ends of the sleepers according to their installation positions. When laying the track, first connect the rail joints, and after the rails are basically adjusted, use a white lead pen to mark the center position of the sleeper on the inside of the rails. Lift the rails with a track lifter, and pad short square wood between the rails and the sleepers. The spacing between the wood is 4 to 5 meters, and the rails are padded. Then, according to the requirements of the design drawings, the sleeper spacing is adjusted so that the sleepers are perpendicular to the rails, and the rubber pads under the rails are placed. Pull out the rail bottom wood so that the rails fall into the rail bearing groove of the sleeper.

[0033] Before installing the fasteners, first square the sleepers, remove the residual residue on the rail groove surface, put the insulating pad under the rail in the right position, then put the gauge baffle seat, gauge buckle plate, spring bar, flat washer, and nut into the rail groove in sequence, use a small crowbar to adjust the fastener to fit tightly in the groove, and finally use an electric wrench to tighten the bolts. The torque of the Type I spring bar fastener is 80N.m~120N.m, and the spring bar can also be placed tightly on the gauge buckle plate at three points.

[0034] In this embodiment, there are three times of track lifting and repair. The first time of track lifting and repair is mainly to fill ballast, eliminate triangular pits and reverse superelevation, and adjust the track position. Specifically, it includes the following contents: (1) Ballasting: Spread the ballast evenly in the track. (2) Track lifting: Lift each track section at several points and pad it with ballast. The track surface after lifting should be roughly smooth, without obvious bumps and reverse superelevation. After lifting, the position of the sleepers should be squared at the same time. (3) Ballasting: After the rail section is lifted, ballast is immediately strung under the sleepers. It is required that the ballast is fully strung and there is no empty hanger. (4) Track shifting: After the above work is completed for a certain length, a track shifting is carried out, that is, the line is shifted to the center line position to achieve straight lines and smooth curves. Before track shifting, check whether the track joints of the line section to be shifted are suitable. If necessary, adjustments should be made to prevent track expansion. Track shifting is based on the outer side lines on both sides. The main purpose of the second round of track raising and maintenance is to fill ballast, level the seams, tamp square sleepers, and further adjust the track position. The specific contents include the following: (1) Ballasting: The same as the first round of track raising and maintenance. (2) Level the seams: When performing this operation, the nuts of the spiral spikes must be loosened to allow the thin square sleepers to be lifted after the track is raised. (3) Track raising: Raise the track to the designed elevation and slightly increase the settlement by 1 to 3 mm. The outer rail of the curve is raised to the required superelevation. The front and rear height and left and right levels of the track after track raising should meet the requirements of the specifications. (4) Thin square sleepers: Align the sleepers according to the markings on the rail waist. (5) Ballasting: The ballast is fully strung within a range of 40 to 50 cm on both sides of the rail. The ballast surface of the 60 cm wide ballast in the middle of the reinforced concrete sleeper should be at least 30 mm lower than the bottom surface of the sleeper. (6) Filling the box: Fill a part of the ballast into the sleeper box for tamping. (7) Tamping: Use a small hydraulic tamping machine to tamp the ballast within 40cm outside and 45cm inside the rail in 3 to 4 times to make the track bed solid so that it can withstand the load when the train passes. (8) Track shifting: Use the outer side line on both sides as the reference to fine-tune the track. Before track shifting, the ballast at the end of the sleeper can be partially removed to reduce the resistance during track shifting. (9) Track leveling: Includes a small amount of track shifting, correcting the line plane position, repairing the track bed, replenishing the ballast in the sleeper box, and compacting the slope and top surface of the track bed to keep it stable. The second track raising and repairing is the final repair of the track bed. This is the last operation before the acceptance of the track project. Its contents include: (1) Track raising: Ensure that the elevation error does not exceed +50mm, -30mm with the elevation specified in the design longitudinal section. The horizontal front and rear height of the track meets the inspection standards, the sleepers are perpendicular to the center line of the line, and the spacing and deflection errors are not greater than ±20mm. (2) Leveling small depressions: Make the track surface smooth. (3) Tamping: There should be no hidden pits and hanging plates at rail joints, and no continuous hidden pits and hanging plates at other places. The hidden pit and hanging plate rate should not exceed 8% for the main line. (4) Track shifting: Straight lines should be straight and curves should be smooth. (5) Filling the ballast in the sleeper box: The ballast surface should be 30mm lower than the top surface of the sleeper, the buried depth of the concrete sleeper should be 150mm, and the middle groove should meet the requirements.(6) Track bed preparation: Tamp the track bed surface to ensure that the track bed cross-section meets the design requirements and the upper and lower edges of the track bed slope are neat and parallel to the rails.

[0035] Taking the project in this embodiment as an example, the project adopts two-way construction from both sides to the center, and efficiently organizes and plans the construction process and plan to achieve rapid construction. The total vibration damping pad of the project is about 6.6 kilometers (design square meters). The cost per square meter is 1,600 yuan, and the saving rate per linear meter is 10%. Then 1,600*10 / 100*6.6*1,000=1,056,000 yuan, and the purchase cost is reduced by about 1,056,000 yuan in total; During the construction period, 1 / 3 of the labor cost is saved per kilometer, about 10 people, and the labor cost standard is an average of 6,000 yuan / month / person. The operation period is 6 months, and the total labor cost is reduced by 696,000 yuan. The net economic benefit is about 1,752,000 yuan.

[0036] In the structural design of subway trackbeds, we began to introduce advanced and mature high-speed railway ballasted vibration-damping pad trackbed technology. Rubber vibration-damping pads have the characteristics of low natural frequency, good vibration reduction effect, fast laying speed, and long service life. Among them, the USM series product design adopts the "sandwich structure + cone truncated type" method, which makes the load and deformation curves show typical nonlinear characteristics and can obtain a stable natural frequency after a certain preload. Urban rail transit rubber vibration-damping pad trackbeds have also been widely used in the field of urban rail transit. The good vibration and noise reduction effects, visual quality, and convenient maintenance have been highly praised in the industry and have been cited by many urban rail transit construction.

[0037] The USM series products adopted in this scheme respond to the national call and are green and pollution-free materials. They achieve low noise, energy saving and environmental protection, high economy, humanized design, rubber vibration damping pads, and are laid on the lower part of the track bed in the form of surface support or strip support. They provide isolation and elasticity between the track and the lower structure, reduce the transmission of wheel-rail vibration to the lower foundation, and are mainly used to reduce the interference of vibration and secondary structural noise generated by train operation on residents or buildings around the line, or protect the building structure from vibration damage. When used on ballasted track beds, they can also improve the stress characteristics of the ballast and delay the overhaul cycle of the line.

[0038] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for constructing a ballasted track bed for urban rail transit based on a shock-absorbing pad, characterized in that: The following steps are involved: S1. Construction preparation: Inspect the construction site to ensure that it meets the construction conditions; S2. Surveying and setting out: Taking the track CPⅢ basic control network as the reference, set out the line center control point, and set out the eccentric control point with the outer deviation distance L of the line center control point. The line connecting the line center control points is the line centerline, and the line connecting the eccentric control points is the outer deviation side line; S3, pouring and curing of the base cushion layer, includes the following sub-steps: (1), cleaning the area within the construction site; (2), after the cleaning is completed, with the line centerline as the center and the outer side line as the boundary, tie the steel bars of the base cushion layer on the roadbed; (3), after the steel bars are tied, install the base cushion layer formwork; (4), after the base cushion layer formwork is installed, pour concrete in the formwork; (5), after the concrete pouring is completed, the base cushion layer is formed, and the base cushion layer is cured until its concrete strength reaches more than 5MPa, the base cushion layer formwork is removed, and the side of the base cushion layer coincides with the outer side line; (6), continue to cure the base cushion layer until its concrete strength is not less than 75% of the design strength, and then proceed to the next step; S4. Laying of vibration damping pads: Lay vibration damping pads on the base cushion layer in a shrinking manner. After the vibration damping pads are laid in place, they are fixed on the base cushion layer. The side edge line outside the laying of the vibration damping pads is the standard for being in place. S5. Track bed laying: ballast, sleepers and rails are laid on the base cushion layer in sequence. The sleepers are positioned based on the outer side line, rail joints are reserved, and then fasteners are installed; S6. Track lifting and repair: After the rails are laid, the various components of the track bed are repaired and the track bed surface is tamped to make the cross-section of the track bed meet the design requirements, and the upper and lower edges of the track bed slope are neat and parallel to the rails, thus completing the track bed construction.

2. The urban rail transit ballasted track bed construction method based on shock-absorbing pads according to claim 1 is characterized in that: In step S1, the inspection of the construction site includes the inspection of the compactness of the roadbed and the flatness of the roadbed surface.

3. The urban rail transit ballasted track bed construction method based on shock-absorbing pads according to claim 2 is characterized in that: The compaction coefficient of the roadbed surface layer is not less than 0.93, and the compaction coefficient of the roadbed bottom layer is not less than 0.

91. The surface flatness of the roadbed surface is not less than ±50 mm.

4. The urban rail transit ballasted track bed construction method based on shock-absorbing pads according to claim 1 is characterized in that: In step S2, the steel bars are at least two layers.

5. The urban rail transit ballasted track bed construction method based on shock-absorbing pads according to claim 1 is characterized in that: The outer deviation distance L is 1 / 2 of the designed width of the base cushion layer.

6. The urban rail transit ballasted track bed construction method based on shock-absorbing pads according to claim 1 is characterized in that: In the step S4, shrinking the edge means that the vibration damping pad is laid in a manner of reducing the width, and the distance between the side edge of the vibration damping pad and the side edge of the base cushion layer is 200-400 mm.

7. The urban rail transit ballasted track bed construction method based on shock-absorbing pads according to claim 1 or 6, characterized in that: The shock-absorbing pads are laid in sections, and adjacent shock-absorbing pads are overlapped at the ends.

8. The urban rail transit ballasted track bed construction method based on shock-absorbing pads according to claim 7 is characterized in that: The overlap width is 20-50 mm.

9. The urban rail transit ballasted track bed construction method based on shock-absorbing pads according to claim 1 is characterized in that: In step S5, the staggered amount of rail joints during rail laying is no more than 40 mm.

10. The urban rail transit ballasted track bed construction method based on shock-absorbing pads according to claim 1, characterized in that: In step S3, the total curing time of the base cushion layer is not less than 7 days.

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