Diversion tunnel side top arch lining steel bar trolley

Abstract

The utility model discloses a diversion tunnel side top arch lining steel bar trolley, and belongs to the technical field of tunnel construction. Comprising a bottom frame and scaffolds arranged on the top face and the side faces of the bottom frame. The scaffold forms a side top arch operation space; and a channel is formed below the bottom frame. The device can be used for reference in the construction stage of lining concrete of the large cavern; moreover, the device not only can be used for lining section steel bar manufacturing and mounting work, but also can be continuously used in drainage hole, grouting and defect treatment periods; the trolley consists of a bottom frame and a scaffold; after operation at one position is finished, the trolley is dragged to the next operation position, the scaffold does not need to be disassembled and assembled frequently, the construction efficiency is high, and the application range is wide.

Description

Technical Field

[0001] The utility model relates to the technical field of tunnel construction, in particular to a diversion tunnel side arch lining steel bar trolley. Background Art

[0002] During diversion tunnel construction, reinforcement fabrication and installation are required before concrete lining. Currently, a large number of steel-formed concrete trolleys are suitable for tunnel side arch lining. However, the conventional method of erecting scaffolding on the tunnel floor and then dismantling it after use is inefficient. Furthermore, there are no referenceable trolley designs and implementation methods for side arch reinforcement installation.

[0003] Therefore, the applicant, based on engineering experience, specially designed a trolley for the lining reinforcement of the diversion tunnel top arch; it is used for reinforcement fabrication and installation operations to improve construction efficiency. Utility Model Content

[0004] The utility model aims to solve the problem of low efficiency in manufacturing and installing the side and top arch reinforcements in the prior art, and proposes a diversion tunnel side and top arch lining reinforcement trolley.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A diversion tunnel side arch lining steel bar trolley comprises a bottom frame and scaffoldings arranged on the top and side surfaces of the bottom frame;

[0007] The scaffolding forms a side-top-arch working space;

[0008] A channel is formed below the bottom frame.

[0009] In some embodiments, the bottom frame is composed of: a plurality of portal frames arranged in parallel, and channel steels fixed to the top and side surfaces of the portal frames to connect all the portal frames into one;

[0010] Travel wheels are provided below the door frame.

[0011] In some embodiments, bottom beams are welded to the lower sides of the door frame;

[0012] The bottom beam is composed of two I-beams arranged opposite to each other on the sides of the wing plates.

[0013] In some embodiments, the portal frame includes: a top beam, a reinforcement beam, two upright posts, two diagonal braces, and a plurality of short braces;

[0014] The top beam and the reinforcement beam are arranged in parallel, and the short braces connect the two;

[0015] The columns are arranged at both ends of the top beam and the reinforcement beam;

[0016] The two diagonal braces are symmetrically arranged in an eight-shaped pattern.

[0017] In some embodiments, the top end of the column is connected to the lower end of the top beam;

[0018] Both ends of the reinforcement beam are connected to the inner side of the column.

[0019] In some embodiments, the outer side of the diagonal brace is further provided with: a short diagonal rod connected to the connection point between the reinforcing beam and the column;

[0020] The upper end portion of the short oblique rod is arranged as a right-angled section.

[0021] In some embodiments, the top of the scaffolding is matched with the top arch and is arranged in a step shape; and is fully paved with bridleways to form a construction platform on the top.

[0022] In some embodiments, the top end of the bottom frame is fixedly provided with vertical ribs corresponding to the steel pipes of the scaffolding.

[0023] In some embodiments, the exterior of the vertical rib is sheathed with an expanding cylinder;

[0024] The top end of the expansion cylinder is chamfered;

[0025] The outer ring of the expansion cylinder is provided with multiple layers of annular grooves, and the annular grooves are fitted with rubber rings protruding outwards;

[0026] The expanding cylinder is provided with a notch.

[0027] In some embodiments, safety nets are hung on the upstream and downstream sides of the scaffolding;

[0028] The top end of the bottom frame is paved with a bridleway board.

[0029] Compared with the prior art, the utility model provides a diversion tunnel side arch lining steel bar trolley, which has the following beneficial effects.

[0030] 1. The utility model provides a trolley for lining steel bars of side and top arch operations, which can be used for reference in the lining concrete construction phase of large caverns. Moreover, it can be used not only for the fabrication and installation of steel bars in lining sections, but also for drainage holes, grouting, and defect treatment.

[0031] 2. The utility model comprises a trolley consisting of a bottom frame and a scaffolding; the bottom frame forms movement and support, and the scaffolding is erected according to the structure of the diversion tunnel to form a working space for personnel; a passage is formed below to ensure the normal passage of construction equipment; after one operation is completed, the trolley can be dragged to the next operation position without the need for frequent disassembly and assembly of the scaffolding, so the construction efficiency is high and the scope of application is wide.

[0032] 3. The utility model is made of common I-beams, square steels and other materials through welding, which has low cost and simple production. The various supporting structures of the door frame are scientific and reasonable, with high overall reliability and strong bearing capacity. Vertical ribs are arranged corresponding to the scaffolding steel pipes, so the installation of the scaffolding is more reliable and the lower end does not shift.

[0033] Other advantages, objectives and features of the present invention will be described in the following description to some extent; and will be apparent to those skilled in the art based on an examination of the following; or may be taught from the practice of the present invention to some extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of the use state of the utility model.

[0035] Figure 2 Schematic diagram of the structure of the bottom frame.

[0036] Figure 3 for Figure 2 Schematic diagram of the enlarged structure at point A in the middle.

[0037] Figure 4 for Figure 2 Schematic diagram of the enlarged structure at point B in the middle.

[0038] Figure 5 This is a front view of the bottom frame.

[0039] Figure 6 This is a structural diagram of the portal frame and channel steel.

[0040] Figure 7 This is a structural diagram of the door frame.

[0041] Figure 8 Schematic diagram of the state of installing the expansion tube for vertical reinforcement.

[0042] Figure 9 Schematic diagram of the explosion state of vertical reinforcement and expansion tube.

[0043] In the picture:

[0044] 1. Bottom frame;

[0045] 2. Scaffolding;

[0046] 21. Horse track board;

[0047] 3. Door frame;

[0048] 31. Top beam; 32. Reinforcement beam; 33. Column;

[0049] 34. Diagonal brace; 35. Short brace;

[0050] 36. Short diagonal stroke;

[0051] 4. Channel steel;

[0052] 5. Travel wheels;

[0053] 6. Bottom beam;

[0054] 7. Standing ribs;

[0055] 8. Expanding cylinder;

[0056] 81. Ring groove; 82. Rubber ring; 83. Notch. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0058] Reference Figure 1-9 A diversion tunnel side arch lining steel bar trolley comprises a bottom frame 1 and scaffolds 2 arranged on the top and side surfaces of the bottom frame 1.

[0059] It should be noted that in order to cooperate with the scaffolding 2 to form a side-top arch working space, the cross-sectional width of the bottom frame 1 must be "at least 3 meters smaller than the lining width of the diversion tunnel"; in order to form a scaffolding installation space of not less than 1.5 meters on both sides; and, in order to cooperate with the bottom chamfer of the diversion tunnel, the bottom ends of the scaffolding on both sides are suspended in the air.

[0060] like Figure 1 As shown, scaffolding 2 is installed on both sides of the bottom frame 1; the lower end of the scaffolding 2 is chamfered to avoid the bottom edge. Preferably, the distance between the scaffolding 2 and the side wall of the diversion tunnel is not less than 0.2m.

[0061] Furthermore, a passage is formed below the bottom frame 1 .

[0062] In order to ensure the normal passage of construction equipment, the clearance height below the bottom frame 1 is not less than 4 meters; preferably, the clearance height below the bottom frame 1 is 5 meters.

[0063] When in use, after the bottom frame 1 is moved to the working position, the scaffolding 2 is erected; the scaffolding 2 is used as a support to carry out the steel bar installation operation; after the operation here is completed, the trolley is dragged as a whole to the next working position.

[0064] In some embodiments, the bottom frame 1 is composed of: a plurality of portal frames 3 arranged in parallel, and channel steels 4 fixed to the top and side surfaces of the portal frames 3 to connect all the portal frames 3 into one.

[0065] like Figure 2 、6 As shown, multiple door frames 3 are matched and connected by channel steels 4.

[0066] Preferably, the channel steels 4 are arranged at intervals of 2 meters, and the contact surfaces are fully welded to ensure reliable connection.

[0067] In some embodiments, the portal frame 3 includes: a top beam 31 , a reinforcing beam 32 , two upright columns 33 , two diagonal braces 34 , and a plurality of short braces 35 .

[0068] The top beam 31 and the reinforcement beam 32 are arranged in parallel; the short support 35 is arranged vertically to connect the two;

[0069] The columns 33 are provided at both ends of the top beam 31 and the reinforcing beam 32;

[0070] The two diagonal braces 34 are symmetrically arranged in an eight-shaped configuration.

[0071] Preferably, the top beam 31 , the reinforcing beam 32 , the upright column 33 , and the diagonal brace 34 are all made of I-beams; the short brace 35 is made of I-beams or square steel; and welding is used between the various structural members.

[0072] Furthermore, the top end of the column 33 is connected to the lower end of the top beam 31 ; and both ends of the reinforcing beam 32 are connected to the inner side of the column 33 .

[0073] like Figure 5 、 7 As shown; the column 33 supports the top beam 31, and the reinforcing beam 32 is connected to the inner side to form a more reliable and stable connection form.

[0074] In addition, the diagonal brace 34 connects the inner side of the column 33 with the lower end of the reinforcing beam 32, and the upper end of the reinforcing beam 32 with the lower end of the top beam 31 to form a reinforced support. Moreover, it pulls the lower part of the column 33 inward to prevent it from expanding and deforming outward, making the overall force more reliable.

[0075] Furthermore, a short diagonal rod 36 connected to the connection point between the reinforcing beam 32 and the column 33 is provided on the outside of the diagonal brace 34 .

[0076] like Figure 5 、 7 short diagonal rod 36 pulls the diagonal brace 34, and supports and strengthens the end of the reinforcement beam 32, so that the whole further has better reliability, and anti-deformation and compressive properties.

[0077] Correspondingly, the upper end of the short oblique rod 36 is set to a right-angle section; one side is connected to the column 33, and the other side is connected to the reinforcing beam 32, and they are firmly welded.

[0078] In addition, running wheels 5 are provided below the gantry 3 .

[0079] Among them, no less than two groups of running wheels 5 are arranged on both sides of the door frame 3.

[0080] Preferably, three groups are provided, each group consisting of two.

[0081] like Figure 2 As shown, 12 running wheels 5 are provided.

[0082] In some embodiments, bottom beams 6 are welded to the lower sides of the door frame 3 .

[0083] like Figure 2 、 4 , 6; the bottom beam 6 is composed of two I-beams arranged opposite to the side edges of the wing; a beam is formed through the bottom end of the bottom frame 1, and has reliable strength.

[0084] Preferably, the top beam 31, the reinforcing beam 32, and the column 33 are all made of I20 I-steel; the channel steel 4 is made of [18 channel steel; and the bottom beam 6 is made of I22 I-steel.

[0085] In some embodiments, the top of the scaffolding 2 is matched with the top arch and is arranged in a step shape; and is fully paved with a bridleway slab 21 to form a construction platform at the top.

[0086] like Figure 1 As shown, a multi-level terrace is formed.

[0087] It should be noted that the distance between the scaffold 2 and the top arch should not be less than 1.8m to allow standing work.

[0088] In addition, safety nets are hung on the upstream and downstream sides of the scaffolding 2; a bridleway board 21 is laid on the top of the bottom frame 1 to prevent tools from falling during installation.

[0089] In some embodiments, the top of the bottom frame 1 is fixedly provided with: vertical ribs 7 corresponding to the steel pipes of the scaffolding 2; when the scaffolding is installed, the steel pipes are placed accordingly and limited; this makes the installation of the scaffolding more reliable and the lower end does not shift.

[0090] The length of the vertical rib 7 is not less than 20 cm to ensure effectiveness.

[0091] like Figure 2 As shown, according to the setting specifications of the scaffolding, the reinforcement 7 is arranged vertically and horizontally.

[0092] Preferably, the spacing between scaffoldings is 1.5m, the row spacing is 1.5m, and the step spacing is 1.5m.

[0093] It should be noted that the vertical reinforcement 7 is made of short steel bars; the outer diameter of the vertical reinforcement 7 is smaller than the inner diameter of the steel pipe.

[0094] For example, the commonly used scaffolding steel pipes have an outer diameter of 48mm and a wall thickness of 3.5mm; the steel bars generally do not exceed 30mm (e.g., 25mm).

[0095] Furthermore, an expanding cylinder 8 is sleeved on the outside of the vertical rib 7 to reduce the gap and enhance stability.

[0096] It can be understood that the outer diameter of the expansion tube 8 is slightly smaller than the inner diameter of the steel pipe of the scaffold 2 .

[0097] like Figure 8 、 9 As shown; the top of the expansion cylinder 8 is set to be chamfered, which is more convenient for the set steel pipe operation.

[0098] In addition, the outer ring of the expansion cylinder 8 is provided with multi-layered ring grooves 81 , and a rubber ring 82 protruding outward is fitted inside the ring grooves 81 ; the rubber ring 82 further enhances stability.

[0099] Furthermore, a notch 83 is provided on the diameter-enlarging cylinder 8 .

[0100] Correspondingly, threaded holes are opened at corresponding positions on the steel pipes of the scaffolding, and bolts are passed through them. The bolts pass through the steel pipes of the scaffolding and the notches 83 of the expansion tube 8 in sequence, and then press against the vertical reinforcement 7 to further enhance the stability of the installation.

[0101] In a diversion tunnel project, the excavated cross-section measured 17m x 21m (width x height). After the standard concrete lining, the net cross-section dimensions were 15m x 19m (width x height). Full-section reinforced concrete lining was used, with a thickness ranging from 0.6m to 1.5m. The concrete lining was divided into 133 sections, each 12m thick.

[0102] After the cavern floor was poured, to improve the efficiency of installing the side arch reinforcement, a side arch reinforcement trolley was designed and fabricated using common resources such as conventional I-beams and steel pipe scaffolding. The efficient use of the concrete lining trolley ensured the safe and orderly fabrication and installation of the side arch reinforcement, achieving the contract objectives of high quality, safety, efficiency, and cost-effectiveness.

[0103] A total of 4 12.2m long side and top arch steel formwork trolleys and 4 13.5m long side and top arch steel bar trolleys are arranged.

[0104] The materials used for each trolley are:

[0105] (1) 17t steel pipe with a diameter of 48mm and a wall thickness of 3.5m:

[0106] (2) 2,650 straight fasteners and 1,300 cross fasteners;

[0107] (3) 64m of I22 I-beam and 468m of I20 I-beam;

[0108] (4) 200m of 25mm diameter steel bars and 5000m² of safety nets for the platform enclosure;

[0109] (5) 4,000 horse treads.

[0110] The entire process of tying the side wall and top arch reinforcement is done manually using a reinforcement trolley.

[0111] The processing and installation deviations of steel bars should be controlled within the range allowed by the specifications. The number of joints of steel bars with the same section should be less than 50%, and the joints of two adjacent steel bars should be staggered by more than 50cm. The steel bar joints should mainly use tapered thread joints and supplemented by manual arc welding.

[0112] The top arch reinforcement is hoisted onto the reinforcement trolley working platform and then installed; during the hoisting process, attention should be paid to the safety of workers and mechanical equipment passing below.

[0113] Various embedded (reserved) pipe fittings required for grouting and drainage holes should be fixed on the lining steel bars in advance using a steel bar trolley and reinforced securely according to the measured and laid-out positions as shown in the drawings.

[0114] During the construction process, four side and top arch reinforcement installation trolleys completed the reinforcement installation work for the lining section 133 of the cavern; they continued to be used during the later drainage hole, grouting and defect treatment, ensuring the construction period. From use to dismantling, the trolleys showed no deformation and the materials can be recycled and reused.

[0115] In this project, the side and top arch reinforcement fabrication and installation trolley was constructed using conventional I-beams, channel steels, automobile tires, scaffolding, etc., which can be used as a reference in similar projects.

[0116] like Figure 1As shown in the cross-section of the reinforced concrete lining of the diversion tunnel, a chamfer with a slope ratio of 1:1 is set between the bottom plate and the side wall; the bottom section is 12m long, and the size after lining is 15m×19m; the running wheels at the bottom of the trolley are arranged in three rows, that is, 6 pairs, 12 in total, with a distance of 1.0m between the ends. They are made of I22 I-beams and automobile wheels with a diameter of 90cm-110cm, and the wheelbase between the wheels is 11m, that is, the span of the portal structure is 11m; the portal structure adopts 9 I20 I-beams arranged at intervals of 1.5m, with a length of 13.5m and a central clearance height of 5m; channel steels are welded on the sides and top of the portal structure to connect it into a whole. The channel steel spacing is mainly 2m, and the first row at the bottom on both sides is 1.25m away from the bottom plate. All contact sections with the portal structure are fully welded and firmly welded; the upper part of the portal structure is fully paved with 5cm thick horseway slabs to prevent falling objects from the top; the contact ends of the steel pipe scaffolding and the portal structure are all inserted into the pre-welded fixed vertical bars, and the row and step spacing between the scaffolding are both 1.5m. A 1m wide pedestrian walkway from the bottom plate to the top of the trolley is set up in the scaffolding. The reserved spacing between the scaffolding and the side walls on both sides is 20cm, and the top is 1.8m to ensure that people can stand when working; the top construction platform is fully paved with 5cm thick horseway slabs, and safety nets are hung on the upstream and downstream sides to prevent tools from falling during installation.

[0117] Main design parameters of the side and top arch reinforcement trolley:

[0118] (1) The design length is 12.2m, and the portal frame structure is made of I20 I-beam; there are 9 gantry frames in total, arranged at intervals of 1.5m; [18 channel steel is used, welded and connected on the sides and top to form a whole, and the clearance height below is 5m to ensure the normal passage of construction equipment;

[0119] (2) The bottom is equipped with walking wheels; there are three rows in total, i.e. 6 pairs, 12 in total; the distance between the two ends is 1.0m, and they are made by welding I22 I-beam and automobile wheels with a diameter of 90cm-110cm;

[0120] (3) With the help of the portal structure, a steel pipe scaffolding is erected to form a side and top arch steel bar installation trolley; the distance between the trolley side wall and the lining wall is 20cm, and the top distance is 1.8m; the spacing of the steel pipe scaffolding is 1.5m, the row spacing is 1.5m, and the step spacing is 1.5m; at the connection between the steel pipe and the portal structure, a steel bar head with a diameter of 25mm and a length of 20cm is welded, and the steel pipe is inserted into the fixed steel bar head. The row spacing between the steel pipes is analyzed and calculated with reference to the fastener-type steel pipe high support frame to ensure the safety of the trolley; the scaffolding rods are made of steel pipes with an outer diameter of 48mm and a wall thickness of 3.5mm, and the performance meets the requirements of Q235A steel in the current national standard "Carbon Structural Steel" GBT700; the fastener performance meets the requirements of "Steel Pipe Scaffolding" GB15831-1995;

[0121] (4) Build a pedestrian walkway on the left or right side starting from the portal frame, with a width of 100 cm and a step distance of no more than 30 cm. It should have double rails and handrails on both sides.

[0122] (5) Safety nets are used to protect the front and rear sides of the trolley operating platform; the scaffolding operating surface is fully covered with 5cm thick bridleways, leaving no gaps or probe plates;

[0123] (6) When a section of steel bars is completed, use a loader to tow it to the next section.

[0124] The utility model provides a trolley for lining steel bars in side and top arch operations, which can be used for reference in the concrete lining construction phase of large caverns. Moreover, the trolley can be used not only for the fabrication and installation of steel bars in lining sections, but can also be used during drainage holes, grouting, and defect treatment.

[0125] In the utility model, the trolley is composed of a bottom frame 1 and a scaffolding 2; the bottom frame 1 forms movement and support, and the scaffolding is erected according to the structure of the diversion tunnel to form a working space for personnel; a passage is formed below to ensure the normal passage of construction equipment; after one operation is completed, the trolley can be dragged to the next operation position, without the need for frequent disassembly and assembly of the scaffolding, with high construction efficiency and a wide range of applications; it is made of common I-beams, square steels and other materials through welding, with low cost and simple production; the various supporting structures of the portal frame are scientific and reasonable, with high overall reliability and strong bearing capacity; vertical ribs 7 are arranged corresponding to the scaffolding steel pipes, so that the installation of the scaffolding is more reliable and the lower end does not shift.

[0126] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention, which should be covered by the protection scope of the present invention.

[0127] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0128] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are illustrative and cannot be understood as limitations on the present invention. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A diversion tunnel side arch lining reinforcement trolley, characterized in that: It comprises a bottom frame (1), and scaffolds (2) arranged on the top surface and side surfaces of the bottom frame (1); The scaffolding (2) forms a side-top arch working space; A channel is formed below the bottom frame (1).

2. The diversion tunnel side arch lining reinforcement trolley according to claim 1 is characterized in that: The bottom frame (1) is composed of: a plurality of door frames (3) arranged in parallel, and channel steels (4) fixed to the top and side surfaces of the door frames (3) to connect all the door frames (3) into one; Travel wheels (5) are provided below the door frame (3).

3. The diversion tunnel side arch lining reinforcement trolley according to claim 2 is characterized in that: Bottom beams (6) are welded to the lower sides of the door frame (3); The bottom beam (6) is composed of two I-beams arranged opposite to each other on the sides of the wing plates.

4. The diversion tunnel side arch lining reinforcement trolley according to claim 2, characterized in that: The door frame (3) comprises: a top beam (31), a reinforcing beam (32), two upright columns (33), two diagonal braces (34), and a plurality of short braces (35); The top beam (31) and the reinforcing beam (32) are arranged in parallel, and the short support (35) connects the two; The upright columns (33) are arranged at both ends of the top beam (31) and the reinforcing beam (32); The two diagonal braces (34) are symmetrically arranged in an eight-shaped arrangement.

5. The diversion tunnel side arch lining reinforcement trolley according to claim 4 is characterized in that: The top end of the column (33) is connected to the lower end of the top beam (31); Both ends of the reinforcing beam (32) are connected to the inner side of the column (33).

6. The diversion tunnel side arch lining reinforcement trolley according to claim 5, characterized in that: The outer side of the diagonal brace (34) is further provided with: a short diagonal rod (36) connected to the connection point between the reinforcing beam (32) and the column (33); The upper end of the short oblique rod (36) is arranged as a right-angled section.

7. The diversion tunnel side arch lining reinforcement trolley according to claim 1, characterized in that: The top end of the scaffolding (2) is matched with the top arch and is arranged in a step shape; and is fully paved with a bridleway board (21) to form a construction platform on the top.

8. The diversion tunnel side arch lining reinforcement trolley according to claim 1, characterized in that: The top end of the bottom frame (1) is fixedly provided with vertical ribs (7) corresponding to the steel pipes of the scaffolding (2).

9. The diversion tunnel side arch lining reinforcement trolley according to claim 8, characterized in that: The exterior of the vertical rib (7) is sheathed with an expanding cylinder (8); The top end of the expanding cylinder (8) is configured to be chamfered; The outer ring of the expansion cylinder (8) is provided with a multi-layered ring groove (81), and a rubber ring (82) protruding outward is sleeved in the ring groove (81); The expanding cylinder (8) is provided with a notch (83).

10. The diversion tunnel side arch lining reinforcement trolley according to claim 1, characterized in that: Safety nets are hung on the upstream and downstream sides of the scaffolding (2); A bridleway board (21) is laid on the top of the bottom frame (1).

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