A ballastless track subgrade anti-differential settlement transition section structure and construction method

Abstract

A ballastless track subgrade differential settlement resistant transition section structure is used to effectively control the differential settlement of the ballastless track bridge approach section and meet the requirements of high-speed railways for line smoothness. It includes a pile-plate transition structure and an embankment transition structure. The pile-plate transition structure is arranged behind the abutment and consists of a pile-plate structure composed of a bearing plate and piles and a first embankment filled between the bearing plate and the foundation. The longitudinal section of the first embankment is trapezoidal. The longitudinal section of the embankment transition structure is trapezoidal, with its front end smoothly connected to the rear end of the first embankment in an inverted trapezoid and its rear end smoothly connected to the embankment of the normal embankment structure in an inverted trapezoid. The main body of the embankment transition structure is a second embankment filled with graded crushed stone. Outside the lateral sides of the second embankment, there are a subgrade body and a bottom layer of the roadbed constructed successively from the foundation upwards, and a surface layer of the roadbed is filled on the bottom layer of the roadbed and the second embankment. The rear part of the bearing plate extends into the embankment transition structure and is supported on the second embankment by overlapping.

Description

Technical Field

[0001] The present invention relates to rail transit, and particularly to a ballastless track subgrade differential settlement resistant transition section structure and construction method. Background Art

[0002] When differential settlement and stiffness differences may occur at the joints between high-speed railway subgrades and other subgrade structures such as bridges and tunnels, different subgrade structures, and different foundation treatment forms, a transition section should be set. The filler of the transition section is filled with graded crushed stone mixed with cement, and the compaction standard is specified. The compaction standard should meet the requirements that the compaction coefficient K≥0.95, the foundation coefficient K30≥150 MPa / m, and the dynamic deformation modulus Evd≥50 Mpa. According to the experience of high-speed railways and highways at home and abroad, a transition section with a certain length is set between the embankment and the bridge to control the gradual change of track stiffness and minimize the track surface deformation caused by uneven settlement between the embankment and the bridge, so as to ensure the high-speed, safe, and comfortable operation of trains.

[0003] Currently, the current specifications have stipulated the structural form and construction method of the transition section, such as the "Code for Design of Railway Subgrade" (TB10001-2016) and the "Code for Design of High-Speed Railway" (TB10621-2014). High-speed railways require the track structure to have high smoothness. The transition section between the subgrade and the bridge is an important part of high-speed railways and has a significant impact on the smoothness of the line. Differential settlement is the main control factor for the smooth and comfortable operation of trains on the transition section. Excessive differential settlement in the transition section will pose a threat to the operation safety of high-speed railways. The ballastless track of high-speed railways has extremely strict control over the differential settlement of the bridge-road transition section. The step caused by settlement difference shall not be greater than 5 mm, and the fold angle caused by uneven settlement shall not be greater than 1 / 1000. In addition, large-scale mechanical compaction construction cannot be carried out near the abutment back of the existing bridge-road transition structure. It is difficult to meet the compaction standard by using small-scale mechanical ramming, which is likely to cause the settlement control index to exceed the limit. Therefore, it is urgent to design a ballastless track subgrade differential settlement resistant transition section structure to solve the above problems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a ballastless track subgrade differential settlement resistant transition section structure to effectively control the differential settlement of the ballastless track bridge-road transition section, while ensuring convenient construction and meeting the requirements of high-speed railways for line smoothness.

[0005] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0006] The present invention discloses a ballastless track subgrade anti-differential settlement transition section structure, which is arranged between a bridge structure and a normal embankment structure, and is characterized in that it comprises a pile-sheet transition structure and a fill transition structure; the pile-sheet transition structure is arranged behind the abutment, and comprises a pile-sheet structure composed of a bearing plate and piles, and a first fill between the bearing plate and the foundation, wherein the piles are arranged at intervals along the horizontal direction, the lower part of the piles penetrates into the foundation bearing layer, and the upper end is consolidated with the bearing plate, the longitudinal section of the first fill is trapezoidal, and the fill is filled with A, B, and C groups of fillers. The longitudinal section of the landfill transition structure is trapezoidal, with the front end connected to the rear end of the first landfill in an inverted trapezoidal shape, and the rear end connected to the normal embankment structure landfill in an inverted trapezoidal shape. The main body of the landfill transition structure is the second landfill filled with graded crushed stone, and the roadbed and the base bed bottom layer are constructed from the foundation upward in sequence on both sides of the second landfill, and the base bed surface layer is filled on the base bed bottom layer and the second landfill; the rear part of the bearing plate extends into the landfill transition structure, and the extended section is overlapped and supported on the second landfill.

[0007] The compaction standard of the first fill body is the compaction coefficient K ≥0.93, foundation coefficient K 30 ≥130MPa / m, small-scale machinery shall be used for compaction within 2.0m behind the abutment, and large-scale machinery shall be used for compaction outside the range of 2.0m behind the abutment.

[0008] The second compaction standard should meet the compaction coefficient K ≥0.95, foundation coefficient K 30 ≥150MPa / m, dynamic deformation modulus Evd ≥50Mpa, use large-scale machinery to compact.

[0009] Another technical problem to be solved by the present invention is to provide a construction method for the above-mentioned ballastless track subgrade anti-differential settlement transition section structure, the method comprising the following steps:

[0010] ① Construction of abutments;

[0011] ② Level the foundation, and construct the first filling body, the second filling body, the road base body and the base bed layer in layers simultaneously. Except for the area within 2.0m behind the abutment, which is compacted by small machinery, the rest of the sections are compacted by large machinery;

[0012] ③Construct the pile-board structure, accurately locate the position of each pile, drill holes to construct the piles, place the pile 3 reinforcement cage and then pour concrete;

[0013] ④ Excavate the foundation pit of the bearing plate, tie the bearing plate steel cage and connect it with the main reinforcement of the pile steel cage, and then pour concrete;

[0014] ⑤Construct the base bed surface.

[0015] The beneficial effects of the present invention are mainly reflected in the following aspects:

[0016] First, a pile - plate transition structure is set at the bridge - roadbed boundary. The first filling body M is used and the pile - plate structure is reinforced to smoothly connect the structural transition between the bridge and the roadbed, which can effectively ensure no differential settlement and stiffness change of the transition structure.

[0017] Second, after the original bridge - roadbed transition section is pushed towards the roadbed direction to the pile - plate transition structure, large - scale machinery can be used for compaction of the filling in the transition section, avoiding differential settlement caused by insufficient compaction of the roadbed filler near the bridge - roadbed boundary by small - scale machinery.

[0018] Third, the filling body transition structure is trapezoidal and a certain filling slope rate is ensured to reduce the influence of the stiffness change between the pile - plate transition structure and the roadbed filling body transition structure on the ballastless track.

[0019] Fourth, it can not only effectively solve the prominent problem of differential settlement in the ballastless track subgrade transition section, but also has simple construction, reasonable economy and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] This specification includes the following three drawings:

[0021] Figure 1 is the longitudinal section view of a ballastless track subgrade differential settlement - resistant transition section structure of the present invention;

[0022] Figure 2 is Figure 1 the sectional view along line I - I in

[0023] Figure 3 is Figure 1 the sectional view along line II - II in

[0024] The figures show the marks and corresponding meanings: abutment 1, bearing plate 2, pile 3, surface layer of subgrade bed 4, bottom layer of subgrade bed 5, roadbed body 6, first filling body M, second filling body N. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be further described below in conjunction with the drawings and embodiments.

[0026] Referring to Figure 1 , a ballastless track subgrade differential settlement - resistant transition section structure of the present invention is set between the bridge structure and the normal embankment structure, and includes a pile - plate transition structure and a filling body transition structure. Referring to Figure 1 and Figure 2, the pile - slab transition structure is arranged behind the abutment 1 and includes a pile - slab structure composed of a bearing plate 2 and piles 3, and a first filling body M filled between the bearing plate 2 and the foundation. The piles 3 are arranged at horizontal intervals, with the lower part penetrating into the foundation bearing stratum and the upper end being consolidated with the bearing plate 2. The longitudinal section of the first filling body M is trapezoidal and is filled with Group A, B, and C fillers. The pile - slab transition structure smoothly connects the structural transition between the bridge and the subgrade, and can effectively ensure no differential settlement and stiffness change in the transition structure. Refer to Figure 1 and Figure 3 , the longitudinal section of the filling - body transition structure is trapezoidal, with the front end smoothly connecting to the rear - end inverted trapezoid of the first filling body M and the rear end smoothly connecting to the rear - end inverted trapezoid of the normal embankment structure filling body. The main body of the filling - body transition structure is a second filling body N filled with graded crushed stone. On both lateral sides of the second filling body N, the subgrade body 6 and the sub - base course 5 are constructed successively from the foundation upwards, and the sub - grade surface course 4 is filled on the sub - base course 5 and the second filling body N. The rear part of the bearing plate 2 extends into the filling - body transition structure, and the extended section is supported on the second filling body N. After shifting the original road - bridge transition section towards the subgrade direction behind the pile - slab transition structure, large - scale machinery can be used for compaction during the transition - section filling, avoiding differential settlement caused by insufficient compaction of the subgrade filler near the road - bridge boundary by small - scale machinery. The first filling body M and the second filling body N transition structures are trapezoidal and ensure a certain filling slope rate, reducing the influence of the stiffness change between the pile - slab transition structure and the subgrade filling - body transition structure on the ballastless track;

[0027] Refer to Figure 1 , the length of the pile - slab transition structure L 1 is the sum of the lengths of two track - slab structures, namely 9.872 m, 10.05 m, or 11.34 m. The filling slope rate of the first filling body M is 1:1, and its bottom length along the line direction a 3 is not less than 2.0 m. The length of the bearing plate 2 extending into the filling - body transition structure a 1 is not less than 1.0 m. The compaction standard of the first filling body M is that the compaction coefficient K ≥0.93 and the foundation coefficient K 30 ≥130 MPa / m. Small - scale machinery is used for ramming and compaction within 2.0 m behind the abutment 1, and large - scale machinery is used for ramming and compaction outside the 2.0 - m range behind the abutment 1.

[0028] Refer to Figure 1 , the length of the filling - body transition structure is not less than 20 m, and its trapezoidal bottom length along the line direction a 2 is not less than 5.0 m. The filling slope rate between the second filling body N and the normal embankment structure filling body nis 1:2. The compaction standard of the second filling body N should meet the compaction coefficient K ≥0.95, the foundation coefficient K 30 ≥150 MPa / m, the dynamic deformation modulus Evd ≥50 Mpa, and large mechanical rolling and ramming are adopted.

[0029] Referring to Figures 1 to 3 , a construction method for a ballastless track subgrade differential settlement resistant transition section structure of the present invention includes the following steps:

[0030] ①Construct the abutment 1;

[0031] ②Level the foundation, and synchronously construct the first filling body M, the second filling body N, the subgrade body 6, and the subgrade bed surface layer 5 in layers. Except for the range within 2.0 m behind the abutment 1 where small mechanical rolling and ramming are used, large mechanical rolling and ramming are used for the rest of the section;

[0032] ③Construct the pile - plate structure, accurately position the positions of each pile 3, drill holes to construct the piles 3, and pour concrete after placing the steel reinforcement cages of the piles 3;

[0033] ④Excavate the foundation pit of the bearing plate 2, bind the steel reinforcement cage of the bearing plate 2 and connect it to the main reinforcement of the steel reinforcement cage of the pile 3, and then pour concrete;

[0034] ⑤Construct the subgrade bed surface layer 4.

[0035] The above is only to illustrate some principles of a ballastless track subgrade differential settlement resistant transition section structure and construction method of the present invention with diagrams, and it is not intended to limit the present invention to the specific structures and application scopes shown and described. Therefore, all possible corresponding modifications and equivalents that can be utilized belong to the scope of the patent applied for by the present invention.

Claims

1. A ballastless track subgrade anti-differential settlement transition section structure, which is set between the bridge structure and the normal embankment structure. Its characteristics are: The invention comprises a pile-sheet transition structure and a compacted body transition structure; the pile-sheet transition structure is arranged behind the abutment (1), and comprises a pile-sheet structure composed of a bearing plate (2), piles (3), and a first compacted body (M) filled between the bearing plate (2) and the foundation; the piles (3) are arranged along the horizontal intervals, the lower part of which penetrates into the bearing layer of the foundation, and the upper end is consolidated with the bearing plate (2); the longitudinal section of the first compacted body (M) is trapezoidal, and is filled with fillers of groups A, B, and C; the longitudinal section of the compacted body transition structure is trapezoidal, and the front end is connected to the first compacted body (M) A back end of a fill body (M) is connected in an inverted trapezoidal shape, and the back end is connected in an inverted trapezoidal shape to a fill body of a normal embankment structure. The main body of the fill body transition structure is a second fill body (N) filled with graded crushed stone. Outside the lateral sides of the second fill body (N) are a road base body (6) and a base bed bottom layer (5) constructed in sequence from the foundation upwards, and a base bed surface layer (4) is filled on the base bed bottom layer (5) and the second fill body (N); the rear part of the bearing plate (2) extends into the fill body transition structure, and the extended section is overlapped and supported on the second fill body (N).

2. A ballastless track subgrade anti-differential settlement transition section structure as claimed in claim 1, Its characteristics are: The length of the pile-slab transition structure L 1 is the sum of the lengths of two track slab structures, namely 9.872m, 10.05m or 11.34m; the filling slope rate of the first filling body (M) is 1:1, and the length of its bottom along the line direction a 3 is not less than 2.0m, and the length of the bearing plate (2) extending into the filling body transition structure a 1 is not less than 1.0m.

3. A ballastless track subgrade anti-differential settlement transition section structure as claimed in claim 2, Its characteristics are: The compaction standard of the first filling body (M) is the compaction coefficient K ≥ 0.93, the foundation coefficient K 30 ≥ 130 MPa / m. Small mechanical rollers are used for ramming and compaction within 2.0 m behind the abutment (1), and large mechanical rollers are used for ramming and compaction outside the 2.0 m range behind the abutment (1).

4. A ballastless track subgrade anti-differential settlement transition section structure as claimed in claim 2, Its characteristics are: The length of the filling body transition structure is not less than 20 m, and the length of its trapezoidal bottom along the line direction ( a 2 ) is not less than 5.0 m. The filling slope ratio ( n ) between the second filling body (N) and the filling body of the normal embankment structure is 1:

2.

5. A ballastless track subgrade anti-differential settlement transition section structure as claimed in claim 4, Its characteristics are: The compaction standard of the second filling body (N) shall meet the requirements of a compaction coefficient K ≥ 0.95, a foundation coefficient K 30 ≥ 150 MPa / m, and a dynamic deformation modulus Evd ≥ 50 Mpa, and large-scale machinery shall be used for rolling and ramming.

6. A construction method for a ballastless track subgrade anti-differential settlement transition section structure according to any one of claims 1 to 5, comprising the following steps: ① Construction of abutment (1); ② Level the foundation and construct the first filling body (M), the second filling body (N), the roadbed body (6) and the base bed (5) in layers simultaneously. Except for the area within 2.0m behind the abutment (1) which is compacted by a small machine, the rest of the sections are compacted by a large machine. ③ construct the pile-board structure, accurately locate the position of each pile (3), drill holes to construct the pile (3), place the pile (3) reinforcement cage and then pour concrete; ④ Excavate the foundation pit of the bearing plate (2), tie the bearing plate (2) steel cage and connect it with the main reinforcement of the pile (3) steel cage, and then pour concrete; ⑤Construct the surface layer of the base bed (4).

Images