Construction method of composite support for upper formwork of cast-in-place bridge across debris flow gully

Abstract

The present invention discloses a construction method for a composite support for the upper formwork of a cast-in-place bridge across a debris flow gully, comprising the following steps: S1, foundation treatment: hardening the construction site; S2, strip foundation construction: casting a plurality of strip foundations at intervals on the foundation in a river channel, and fixing steel plates on the strip foundations; S3, steel pipe pile column construction: fixing the steel pipe column on the steel plate; S4, I-beam construction: arranging two I-beams at intervals on the steel pipe column in the transverse direction of the bridge, and arranging an electric hydraulic jack next to the steel pipe column; S5, Bailey beam construction: installing the Bailey beam on the I-beam; S6, support installation: installing a socket-type full-bridge support above the Bailey beam, and connecting the electric hydraulic jack to the disc-type full-bridge support; the present application uses the disc-type full-bridge support set on the Bailey frame on the river channel to cross the gully at one time, which is conducive to the normal passage of debris flow and avoids the damage and influence of gully flood discharge on bridge construction.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, and in particular to a construction method for a composite support for upper formwork of a cast-in-place bridge spanning a debris flow gully. Background Art

[0002] Some riverbeds are seasonal debris flow gullies. These gullies are drained seasonally and, while dry during normal times, are prone to natural disasters such as debris flows after heavy summer rains. The geological and hydrological conditions are complex and harsh. For bridges spanning these seasonal debris flow gullies, preventing the destruction of cast-in-place bridge supports by such disasters during construction is a pressing issue. Summary of the Invention

[0003] In view of the defects in the prior art, the purpose of the present invention is to provide a construction method for a composite support for the upper formwork of a cast-in-place bridge spanning a debris flow gully.

[0004] The technical solution adopted in the present invention is:

[0005] The construction method of the upper formwork composite support of the cast-in-place bridge across the debris flow gully includes the following steps:

[0006] S1. Foundation treatment: Level the construction site of the bridge support and then perform hardening treatment;

[0007] S2. Strip foundation construction: Multiple strip foundations are cast at intervals on the hardened foundation in the river channel, and steel plates are fixed on each strip foundation;

[0008] S3. Steel pipe pile column construction: fixing the bottom of the steel pipe column on the steel plate to connect with the strip foundation;

[0009] S4. I-beam construction: two I-beams are spaced apart in the transverse direction of the steel pipe columns as main beams, and electric hydraulic jacks are installed next to the steel pipe columns;

[0010] S5. Bailey beam construction: Install the pre-connected Bailey beams onto the I-beam main beams;

[0011] S6. Bracket installation: A socket-type full-bridge bracket is installed above the Bailey beam, and a top support is provided on the bracket. The top support is connected to the Bailey beam piece through a single buckle frame; the electric hydraulic jack is connected to the buckle frame.

[0012] Furthermore, after the bracket is installed, the following steps are also included:

[0013] S7. Pre-pressing the support: laying an I-beam on the support, laying scaffolding or steel formwork on the I-beam, pre-pressing the scaffolding or steel formwork with sandbags, and unloading the sandbags after pre-pressing is completed.

[0014] Furthermore, in step S1, the construction site of the bridge support is leveled and hardened, specifically:

[0015] After the site is rolled and leveled, the foundation bearing capacity is tested. If the foundation bearing capacity reaches 200Kpa, a 20cm thick layer of C25 strength concrete is poured on the repaired foundation for hardening treatment.

[0016] Furthermore, a concrete bottom seal is provided around the bottom of each strip foundation, the thickness of the concrete is 10 cm, and the strength is C25.

[0017] Furthermore, the steel plates are fixed by expansion bolts or embedded steel bars by welding.

[0018] Furthermore, triangular steel plates are welded around the bottom of the steel pipe column.

[0019] Furthermore, the pre-compression weight is 1.2 times the deadweight of the cast-in-place box girder.

[0020] Furthermore, the preload is divided into three times of loading, the first loading weight is 60% of the preset deadweight of the beam body, the second loading is performed after the load is stable, the second loading weight is 80% of the preset deadweight of the beam body, and the third loading is performed after the load is stable, the loading weight is 120% of the deadweight of the beam body.

[0021] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. DETAILED DESCRIPTION

[0022] The following embodiments of the technical solution of the present invention will be described in detail with reference to specific embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only used as examples and are not intended to limit the scope of protection of the present invention.

[0023] It should be noted that, unless otherwise specified, the technical or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0024] The present application discloses a construction method for a composite support structure for the upper formwork of a cast-in-place bridge across a debris flow gully, comprising the following steps:

[0025] S1. Foundation treatment: Level the construction site of the bridge support and then harden it.

[0026] The bridge consists of three spans, namely the first span, the second span and the third span. The first span and the second span both cross the highway and can be box girder structures; the third span is located between the first span and the second span, and the third span crosses the riverbed and is a Bailey beam structure.

[0027] According to the design plan, the foundation position is measured using a total station and a steel ruler, grooves and leveling are done using machinery in conjunction with manual labor, and the foundation is compacted with water using a roller.

[0028] The construction sites for the first, second, and third spans of the bridge support were refinished and leveled, and the foundation bearing capacity was tested. If the foundation bearing capacity reached 200 kPa, a 20 cm thick layer of C25 strength concrete was poured on the refinished foundation for hardening.

[0029] The poured concrete is sloped to facilitate drainage, and drainage ditches are installed along the edges of the foundation to drain water into the riverbed, ensuring that the foundation is not affected by accumulated water and maintaining its overall bearing capacity. Hardened concrete is poured in sections or with continuous joints to prevent arching due to temperature differences.

[0030] S2. Strip foundation construction: Multiple strip foundations were cast at intervals on the hardened ground within the river channel, with steel plates fixed to each strip foundation. A 10cm thick, C25 strength concrete seal was applied around the bottom of each strip foundation to prevent heavy rain from eroding the strip foundation and causing the support to become unstable.

[0031] The strip foundation is 1m high and 1.5m wide, and its length extends outward by 1 to 2m according to the projection line of the flange plate of the Bailey beam.

[0032] A steel plate is set on the strip foundation and fixed with expansion bolts or embedded steel bars by welding; the plane size of the steel plate is 75x80cm, the thickness is 1.2cm, and the steel plate is set horizontally.

[0033] S3. Construction of steel pipe pile columns: Weld the bottom of the steel pipe column to the steel plate to connect it to the strip foundation, and weld triangular steel plates around it to enhance the stability of the steel pipe column.

[0034] The steel pipe columns are Φ630mm*8mm steel pipe columns, and a 25T truck crane is used for installation.

[0035] S4. I-beam construction: Two 45C I-beams are set at intervals in the transverse direction of the steel pipe column as the main beam. When installing the I-beam, ensure that the center of the I-beam coincides with the center of the steel pipe column. During the construction of the steel pipe column, pay attention to the control of vertical verticality.

[0036] A large-capacity electric hydraulic jack is installed next to the steel pipe column to precisely control the Bailey beam elevation. The electric hydraulic jack model is DYG200-500 and is arranged horizontally. During installation, the lifting center of gravity and the jack's point of force must be controlled according to the jack's operating requirements. After jacking to the designed elevation, the steel pipe column is used as the load support. The jack should not be subjected to the force alone to prevent overturning.

[0037] S5. Bailey beam construction: Install the pre-connected Bailey beams onto the I-beam main beam.

[0038] The Bailey beam adopts the domestically produced "321" highway steel bridge truss (3x1.5m), and its longitudinal length is arranged according to the span of the box beam; single-layer Bailey beams are arranged at 90cm under the transverse section web and the flange plates at both ends, and at 60cm under the rib plates. Each group of beams is composed of several Bailey beams. The longitudinal distance of 3m between the beams in each group is connected by a matching support frame as a transverse connection, and the groups are connected by connecting plates. In this way, the entire Bailey beam is connected into a whole, so that the force of each row of Bailey beams is balanced; the longitudinal and transverse slopes of the box beam are adjusted by adjusting the electric hydraulic jacks set next to the steel pipe columns.

[0039] Bailey beams are pre-assembled and connected on the ground in groups. The positions of the Bailey beams are marked with red paint on the transverse I-beams at the required spacing. A truck crane is used to lift the connected Bailey beams into place, first in the center and then on the sides. When lifting a single row of Bailey beams, two lifting points must be set up, evenly spaced, to maintain balance during the lifting process and avoid distortional stress.

[0040] S6. Bracket installation: A socket-type full-bridge bracket is installed above the Bailey beam. A top support is provided on the bracket. The top support is connected to the Bailey beam piece through a single disc bracket. The electric hydraulic jack is connected to the disc bracket. The longitudinal and transverse slopes of the box beam are adjusted by the electric hydraulic jack.

[0041] Specifically, a socket-and-spigot full-frame support is installed above the Bailey beam. A top support is placed on the support. Channel steel ribs, timber ribs, and bottom formwork are then installed on the top support. The bottom formwork is laid piece by piece and interconnected. The channel steel ribs, timber ribs, and bottom formwork are then installed using conventional construction methods. A single screw-and-hook bracket connects the top support to the Bailey beam. Rubber strips are inserted between the formwork panels during installation to prevent leakage during concrete pouring, which could affect the beam's appearance.

[0042] S7. Pre-pressing the support: laying an I-beam on the support, laying scaffolding boards or steel formwork on the I-beam, pre-pressing the scaffolding boards or steel formwork with sandbags, and unloading the sandbags after pre-pressing is completed.

[0043] In order to prevent the plywood from being damaged during the hoisting of the pre-compression sand bags and affecting the appearance quality of the cast-in-place box girder concrete, wooden squares and plywood are not laid on the bracket during pre-compression. Instead, scaffolding (or steel formwork) is used on the I-beam instead. After the bracket is qualified for pre-compression, the scaffolding is unloaded and removed, and then square timber and plywood are laid as required to proceed to the next construction process.

[0044] Sandbag preloading is used, and the preloading weight is 1.2 times the deadweight of the cast-in-place box girder. The sandbags are preloaded manually with a crane. For example, if the deadweight of the concrete is 1052 tons, 1.2 times is 1262 tons. The data represents the preloading results of the support with the same erection method.

[0045] The above method is used to pre-compress the support, eliminating the inelastic deformation of the support and the inelastic settlement of the foundation, obtaining the elastic deformation data of the support under load, and determining the reasonable construction pre-arch, so that the box girder can obtain the elevation and shape that meet the design after the support is removed.

[0046] Preloading is carried out after the support is erected and the baseboard scaffolding is laid. During preloading, loading is carried out in three steps. The first loading weight is 60% of the preset deadweight of the beam. After the load is stable, the second loading weight is applied, and the second loading weight is 80% of the preset deadweight of the beam. After the load is stable, the third loading weight is applied, and the loading weight is 120% of the deadweight of the beam.

[0047] During loading, sandbags were transported vertically by a 25T truck crane, and the order of sandbag placement was consistent with the concrete pouring sequence. Observation points were set up at 1 / 2 and 1 / 4 of each span's length, at the pier, and at the strip foundation of each row of steel pipe columns. Before loading, observation rods were installed at each observation point, and the top elevation of the rods was measured. After loading, settlement observations were conducted using a level.

[0048] Specifically, after the first loading, observations are made every two hours. When the settlement is observed to be no more than 3 mm for two consecutive times and is zero, a second loading is performed and the above steps are repeated until the third loading is completed.

[0049] After all loading is completed, the support pre-compression monitoring is carried out. When the average settlement of each observation point in the first 72 hours is less than 5mm, the support pre-compression is determined to be qualified and the pre-compression sandbags can be unloaded. Otherwise, the load must be maintained for pre-compression until the average settlement of the foundation and the support is less than 5mm.

[0050] Unloading is done manually with the help of a crane to lift sand bags for uniform unloading, and the unloading can be completed in one go.

[0051] This application uses a Bailey frame to set up a disc-type full-bridge support on the river channel to cross the gully in one go, which is conducive to the normal passage of debris flow, avoids the damage and impact of gully flood discharge on bridge construction, and prevents excessive disasters from destroying the full-bridge support of the cast-in-place bridge; the disc-type support is used to adjust the elevation of the bottom formwork of the cast-in-place box girder, and the top support is equipped with a channel steel frame combined with double-layer wooden planks as support. A hydraulic support is set at the bottom of the Bailey frame to adjust the design elevation of the Bailey frame and the entire bridge, thereby achieving precise adjustment of the design elevation.

[0052] In this application, unless otherwise specified or limited, the terms "connected," "connect," "fixed," and the like should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0053] In the description of the present invention, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, systems, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0054] In the description of this specification, the reference terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, systems, 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, systems, 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.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. The construction method of the upper formwork composite support of the cast-in-place bridge across the debris flow gully is characterized by: The steps include: S1. Foundation treatment: Level the construction site of the bridge support and then perform hardening treatment; S2. Strip foundation construction: Multiple strip foundations are cast at intervals on the hardened foundation in the river channel, and steel plates are fixed on each strip foundation; S3. Steel pipe pile column construction: fixing the bottom of the steel pipe column on the steel plate to connect with the strip foundation; S4. I-beam construction: two I-beams are spaced apart in the transverse direction of the steel pipe columns as main beams, and electric hydraulic jacks are installed next to the steel pipe columns; S5. Bailey beam construction: Install the pre-connected Bailey beams onto the I-beam main beams; S6. Bracket installation: A socket-type full-bridge bracket is installed above the Bailey beam, and a top support is provided on the bracket. The top support is connected to the Bailey beam piece through a single buckle frame; the electric hydraulic jack is connected to the buckle frame.

2. The construction method of the upper formwork composite support of the cast-in-situ bridge across the debris flow gully according to claim 1 is characterized in that: After the bracket is installed, the following steps are also included: S7. Pre-pressing the support: laying an I-beam on the support, laying scaffolding boards or steel formwork on the I-beam, pre-pressing the scaffolding boards or steel formwork with sandbags, and unloading the sandbags after pre-pressing is completed.

3. The construction method of the upper formwork composite support of the cast-in-situ bridge across the debris flow gully according to claim 1 is characterized in that: In step S1, the construction site of the bridge support is leveled and then hardened, specifically: After the site is rolled and leveled, the foundation bearing capacity is tested. If the foundation bearing capacity reaches 200Kpa, a 20cm thick layer of C25 strength concrete is poured on the repaired foundation for hardening treatment.

4. The construction method of the upper formwork composite support of a cast-in-situ bridge across a debris flow gully according to claim 1 is characterized in that: A concrete bottom seal is provided around the bottom of each strip foundation, the thickness of the concrete is 10 cm, and the strength is C25.

5. The construction method of the upper formwork composite support of a cast-in-situ bridge across a debris flow gully according to claim 1 is characterized in that: The steel plates are fixed by expansion bolts or pre-buried steel bar welding.

6. The construction method of the upper formwork composite support of a cast-in-situ bridge across a debris flow gully according to claim 1 is characterized in that: Triangular steel plates are welded around the bottom of the steel pipe column.

7. The construction method of the upper formwork composite support of a cast-in-situ bridge across a debris flow gully according to claim 2 is characterized in that: The preloading weight is 1.2 times the deadweight of the cast-in-place box girder.

8. The construction method of the upper formwork composite support of a cast-in-situ bridge across a debris flow gully according to claim 2 is characterized in that: The preloading is carried out three times, the first loading weight is 60% of the preset deadweight of the beam body, the second loading is carried out after the load is stable, the second loading weight is 80% of the preset deadweight of the beam body, the third loading is carried out after the load is stable, and the loading weight is 120% of the deadweight of the beam body.