A construction method for an assembled traffic bridge at a flood discharge opening

Abstract

The present invention discloses a construction method for an assembled traffic bridge at the flood discharge hole, which is constructed by the method of making a curved bridge straight, and includes the following steps: 1) Construction of abutments and piers; the construction of abutments includes the steps of abutment foundation excavation, anchor rod construction, foundation pouring construction, abutment body pouring construction, abutment cap pouring construction and backfill of the abutment; in the step of backfill of the abutment, the backfill operation is carried out in two construction periods. The first construction period is to construct the abutment body to the flood season water level elevation; the second construction period is to carry out the backfill of the abutment for the part of the abutment body above the flood season water level elevation after the construction of the abutment body is completed; 2) Construction of capping beams; 3) Prefabrication construction of T-beams; 4) Construction of the bridge deck. The construction method of the present invention aims at the special construction scenario of the flood discharge hole in the flood discharge system of the hydropower station, fully considers the special environmental factors on the construction site of the construction scenario, and can well ensure the normal construction of the traffic bridge in the flood season and rainy season, so as to meet the requirements of the construction period and progress of the traffic bridge.

Description

Technical Field

[0001] The invention belongs to the technical field of road and bridge construction, and particularly relates to a construction method for an assembled traffic bridge at a flood discharge hole. Background Art

[0002] During the construction project of a certain hydropower station's flood discharge system, it is necessary to construct a traffic bridge at the outlet of the shaft flood discharge tunnel. As Figure 1 shown, there is a suspension at the intersection of the preset position of the traffic bridge abutment and the upstream inner slope of the access tunnel at the construction position of the traffic bridge; meanwhile, during the construction of the traffic bridge abutment, the impact of the flood season on the abutment construction needs to be considered, which all pose certain difficulties to the construction of the traffic bridge at the flood discharge tunnel outlet. Summary of the Invention

[0003] The purpose of the invention is to provide a construction method for an assembled traffic bridge at a flood discharge hole, so as to solve the problem that it is difficult to construct a traffic bridge at the flood discharge hole due to the limitation of on-site construction conditions during the construction process of the hydropower station's flood discharge system.

[0004] The invention is realized through the following technical solutions:

[0005] A construction method for an assembled traffic bridge at a flood discharge hole, which is constructed by the method of making a curved bridge straight, and includes the following steps:

[0006] 1) Construction of the abutment and pier; the construction of the abutment includes the steps of abutment foundation excavation, anchor rod construction, foundation pouring construction, abutment body pouring construction, abutment cap pouring construction, and backfilling of the abutment;

[0007] During the backfilling step of the abutment, the backfilling operation is carried out in two construction periods. The first construction period is to construct the abutment body to the flood season water level elevation, and during this construction period, the back of the abutment and the surrounding area are backfilled every time a bin is poured during the pouring process of the abutment body; the second construction period is after the construction of the abutment body is completed, and the part of the abutment body above the flood season water level elevation is backfilled;

[0008] 2) Construction of the capping beam;

[0009] 3) Prefabrication construction of the T-beam;

[0010] 4) Construction of the bridge deck.

[0011] On the other hand, in the construction method of the invention, during the backfilling step of the abutment, during the first construction period, the back of the abutment is backfilled to 50 cm below the elevation of the bin surface every time a bin of the abutment body is poured;

[0012] During the construction of the abutment, for the part below the flood season water level elevation, the pouring construction is carried out in multiple bins, including: foundation pouring construction, and the pouring height is the height of the abutment foundation; the pouring of the abutment body is carried out in multiple bins, and the construction height of each bin is the same and does not exceed 1 / 3 of the overall construction height.

[0013] On the other hand, in the construction method of the present invention, during the foundation pouring construction and the abutment body pouring construction, the formwork support is erected in a layered manner. After the pouring of each bin is completed, the formwork support is removed, and the backfill of the abutment is carried out. On the basis of the backfill, the formwork support is erected, and then the pouring construction of the next bin is carried out;

[0014] During the foundation pouring construction, the erection height of the formwork support should be greater than the height of the abutment foundation. During the pouring construction of each bin of the abutment body, the erection height of the formwork support should be greater than the height of each bin of the pouring construction.

[0015] On the other hand, in the construction method of the present invention, after the foundation excavation is completed, the positions of the foundation anchor bars and bolts are marked out. The foundation anchor bars and bolts are mortar bolts with a certain specified diameter. The buried depth of the bolts is not less than 3m, and the exposed length is not less than 1.0m. The foundation anchor bars and bolts are arranged in multiple rows and not less than 3 rows. The number of bolts in each row is not less than 27, and the spacing between each row is not more than 1.0m.

[0016] On the other hand, in the construction method of the present invention, the abutment pouring construction uses wooden formwork. Before the formwork installation, the formwork is assembled into a whole. When assembling, the misalignment of the formwork joints does not exceed 1mm, and a sponge strip is clamped between the joints;

[0017] The assembled formwork is installed at the construction position. After the formwork is installed in place, it is supported by pipe racks and timbers and fixed using the abutment body steel bars;

[0018] During the construction of the abutment body by pouring in bins, after the installation of the construction formwork for each bin is completed, according to the abutment side lines and axes released on the concrete cushion or the concrete surface of the previous bin, the position of the formwork is initially adjusted, including the adjustment of the formwork diagonal and perpendicularity. The adjustment of the formwork diagonal is to adjust the side formwork of the formwork to be roughly coincident with the abutment side line; after the initial adjustment is completed, the formwork is finely adjusted until the formwork installation meets the design requirements.

[0019] On the other hand, in the construction method of the present invention, after the formwork installation is completed, supports are added outside each side formwork to reinforce the formwork. After the formwork is processed, the top elevation of the concrete in this bin is measured and marked every 2m on each side formwork.

[0020] On the other hand, in the construction method of the present invention, during the abutment body pouring construction, the concrete pouring is carried out in a layered connection manner. The layer thickness is 30 - 50cm, and each layer is vibrated compactly;

[0021] The vibration operation uses an insertion-type vibrator. The vibration positions are controlled in a quincunx pattern, and the spacing is not more than 1.5 times the effective vibration radius; when vibrating the upper layer, it is inserted into the lower layer by about 5 - 10cm to make the upper and lower layer concretes closely combined;

[0022] After the concrete in each bin has initially set, roughen the top surface of the concrete and remove the floating slurry on the surface.

[0023] On the other hand, in the construction method of the present invention, slope-concrete in combination with cable anchors is used for construction under the abutment.

[0024] On the other hand, in the construction method of the present invention, the area between the access tunnel entrance and the abutment is backfilled with C25 rubble concrete.

[0025] The construction method of the present invention is aimed at the special construction scenario of the flood discharge tunnel in the hydropower station flood discharge system, fully considering the special environmental factors at the construction site of the construction scenario, formulating a targeted construction plan, and being able to well ensure the normal construction of the traffic bridge during the flood season and the rainy season, so as to meet the requirements of the construction period and progress of the traffic bridge.

[0026] During the construction of the abutment, the combined method of pouring in bins, backfilling the abutment back in bins, and erecting the pouring support in bins is adopted for the above-mentioned construction environment, which can well ensure the normal construction of the abutment and the construction quality of the abutment. Brief Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic diagram of the construction position of the prefabricated traffic bridge for the flood discharge tunnel of the present invention. Detailed Embodiments

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0030] In the project of a certain hydropower station flood discharge system, it is necessary to erect a traffic bridge at the outlet of the flood discharge tunnel. There is a suspension at the intersection of the preset position of the traffic bridge abutment and the inner upstream slope of the access tunnel entrance, which makes the construction of the abutment at this position difficult and it is difficult to ensure the construction quality of the abutment, thus affecting the construction quality of the entire traffic bridge. At the same time, due to the environmental factors at the location of the traffic bridge abutment during construction, the problem of the impact of the flood season on the abutment construction needs to be considered.

[0031] In view of the technical problems existing in the construction of the traffic bridge erected at the flood discharge hole, a construction method for an assembled traffic bridge is provided in this embodiment.

[0032] According to the on-site construction conditions, the erection construction of the traffic bridge adopts the method of constructing a curved bridge as a straight bridge. After the construction of the abutment and pier is completed, prestressed concrete T-beams are erected, with an oblique angle of 30°.

[0033] In view of the problem of suspension at the intersection of the lower part of the traffic bridge abutment and the upstream inner slope of the access tunnel, the construction is carried out by means of slope-concrete in combination with cable anchors under the abutment to ensure the construction dimensions and quality of the abutment.

[0034] Due to the construction method of constructing a curved bridge as a straight bridge, the triangular area between the access tunnel entrance and the No. 1 abutment is backfilled with C25 rubble concrete.

[0035] Specifically, the construction method adopted in this embodiment is described in combination with specific engineering construction, including the following steps:

[0036] 1) Construction of abutment and pier; the abutment construction includes the steps of abutment foundation excavation, anchor rod construction, foundation pouring construction, abutment body pouring construction, abutment cap pouring construction and backfill of the abutment back;

[0037] Taking Figure 1 the No. 0 abutment shown in

[0038] as an example, the traffic bridge abutment consists of a foundation, an abutment body, an abutment cap, seismic isolation blocks and side walls, etc. Among them, the foundation size is 2943×1240×200 cm, the abutment body size is 2712×820×1800 cm, the top elevation of the abutment foundation excavation is 2255 m, the bottom elevation is 2253 m, and the height difference is 2.0 m.

[0039] a) Foundation excavation and foundation anchor bar construction:

[0040] According to the procedure, the excavation boundary line and control points of the foundation are released. During the excavation process, the excavation slope boundary line and elevation are measured. When excavating to about 30 cm above the base elevation, manual cleaning is carried out to the bedrock.

[0041] According to the drawing, the total station is used to release the coordinate positions of the foundation anchor bars, and the positions are rechecked; the foundation anchor bars adopt ∅22 mortar anchor bars, with a length of 4.5 m and an exposed length of 1.0 m; a hand-held pneumatic drill is used for drilling, and the drilling depth is 3.5 m; the mortar anchor bars are arranged in three rows, with a spacing of 1.0 m between each row, 27 roots are arranged in each row, and they are arranged at equal intervals, with a total of 81 roots.

[0042] b) Formwork installation: For the casting construction of the abutment, wooden formwork is used. Before formwork installation, the formwork is assembled into a whole. When assembling, the joint offset does not exceed 1 mm, and a sponge strip is clamped between the joints to prevent slurry leakage.

[0043] After the formwork is installed in place, pipe supports and round logs or square timbers are used for support, and it is fixed with the abutment body reinforcement.

[0044] After the formwork for each bay is assembled, the construction workers initially adjust the formwork according to the abutment edge line and axis that have been marked on the concrete cushion or the concrete surface of the previous bay, and adjust the diagonal and perpendicularity of the formwork; the adjustment of the diagonal of the formwork is to adjust the side formwork of the formwork to be roughly coincident with the abutment edge line; the adjustment of the perpendicularity is assisted by the measurement of perpendicularity; after the initial adjustment is completed, the surveyors finely adjust the formwork until the formwork meets the design and specification requirements.

[0045] After the formwork adjustment is completed, supports are added outside each side formwork to reinforce the formwork. After the formwork reinforcement is completed, the top elevation of the concrete for this bay is measured and lofted every 2 m on each side formwork and marked, which is used as the control basis for the top surface of the cast concrete.

[0046] c) Foundation, abutment body casting construction and backfill construction of the abutment:

[0047] The foundation and abutment body casting construction adopts a bay construction method. For the reinforced concrete part below the flood season water level elevation, it is cast in 4 bays, namely, the foundation casting height is 2 m (elevation EL.2255 m), the first bay of the abutment body casting height is 3 m (elevation EL.2258 m), the second bay of the abutment body casting height is 3 m (elevation EL.2261 m), and the third bay of the abutment body casting height is 3 m (elevation EL.2264 m).

[0048] The concrete pouring for the foundation and abutment body casting construction is carried out continuously in layers. The layer thickness is controlled within 30 - 50 cm, and each layer is vibrated compactly to prevent vibration omission and over-vibration; an insertion vibrator is used for vibration. The vibration positions are controlled in a plum blossom shape, and the spacing is not greater than 1.5 times the effective vibration radius; when vibrating the upper layer, it is inserted 5 - 10 cm into the lower layer to make the upper and lower layer concretes closely combined. The vibration degree is appropriate when fine slurry is produced and there are no air bubbles or water bubbles on the surface; when the vibrator is lifted out of the concrete, it should be slow to prevent cavities from forming in the concrete; after the concrete in each bay starts to set, the top surface of the concrete needs to be roughened in time, and the surface floating slurry is cleaned.

[0049] The backfill of the abutment in the abutment construction is carried out in two construction periods. The first construction period is to construct the abutment body above the flood season water level elevation (EL.2265 m). During this process, for each bay cast, the backfill of the abutment and its surrounding areas is carried out to prevent the river water from flowing back into the construction operation area after the river water rises; the second construction period is to backfill the part above the flood season water level elevation after the abutment body construction is completed.

[0050] During the backfill construction of the abutment, within the first construction period, for each bay of the abutment wall poured, the backfill is carried out to a height 50 cm below the elevation of the poured bay surface.

[0051] Since the outside of the abutment is a river, for the convenience of abutment construction and to prevent river water from flowing back into the construction area during construction, during the pouring construction of the foundation and the abutment wall, for the part with an elevation below the flood season water level elevation (EL.2265m), a combined method of sectional backfill and sectional erection of the pouring support is adopted; after each bay is poured, the pouring support is removed and backfilled, and then the construction of the next bay is carried out; for the part with an elevation above (EL.2265m), it is gradually increased according to the pouring height, and the total erection height is 8.8m.

[0052] During this construction process, an operation platform support with a height of 3m is erected for the foundation pouring construction, and a pouring support with a height of 4m is erected for each bay of the abutment wall pouring construction; the erection method of the pouring support is: using the ∅16 screw rods during the concrete pouring process to weld with the inner horizontal bars of the pouring support to ensure the overall stability of the erection of the pouring support.

[0053] After the construction of each bay of concrete is completed, the pouring support needs to be removed, and then the backfill of the abutment and the backfill of the stone slag on the upstream and downstream sides are carried out.

[0054] 2) Capping beam construction;

[0055] The capping beam adopts a combined steel formwork. Steel corbels are set on the pier, and two I-beams are erected on the steel corbels as the load-bearing structure; square timbers are horizontally laid on the I-beams, and the bottom formwork is erected on the square timbers for the construction of the capping beam.

[0056] 3) Prefabrication construction of T-beams;

[0057] In this project, the prestressed concrete T-beams are constructed by the method of on-site prefabrication. The concrete of the T-beams (hollow slab beams) is poured continuously, and horizontal layered pouring is adopted, with the material being fed and vibrated layer by layer, and the thickness of each layer not exceeding 30 cm. Since there are many embedded parts and reinforcement bars at the positions of the prestressed anchors of the T-beams, small-aggregate concrete can be used for pouring during pouring, and sufficient vibration is carried out to ensure the compactness of the concrete. After the concrete pouring is completed, it is covered with plastic film or straw curtains and cured by sprinkling water. The curing time is 28 days. During the curing period, the concrete should always be kept in a moist state. When the temperature is lower than 5℃, steam heating with a warm shed is adopted for curing.

[0058] Vibration shall be carried out using ∅80 - ∅100 internal vibrators. For parts with dense steel bars and corners, ∅30mm flexible hoses shall be used for vibration. The vibration time shall be based on when the concrete no longer significantly subsides, no bubbles appear, and the concrete starts to show surface paste; the moving distance of the vibrator shall not exceed 1.5 times its effective radius, and it shall be inserted into the lower layer of concrete by 5 - 10cm, in sequence and in the same direction, to avoid over-vibration, missed vibration or under-vibration.

[0059] When the concrete strength of the T-beam reaches 90% of the designed concrete strength grade and the concrete age is not less than 15 days, the tensioning construction of the prestressed steel tendons shall be carried out.

[0060] After the tensioning construction of the prestressed steel tendons on the T-beam is completed, the grouting construction operation shall be carried out, including the following steps:

[0061] a) Mixing of cement slurry: The water-cement ratio of the cement slurry shall be between 0.40 - 0.45, the bleeding rate of the cement slurry shall not exceed 3% at most, and the bleeding rate after 3h of mixing shall be controlled within 2%;

[0062] Water reducing agents can be added to the cement slurry mixture. The water-cement ratio of the cement slurry with water reducing agents added can be reduced to 0.35;

[0063] A certain amount of expansive agent can be added to the cement slurry. The performance and usage method of the expansive agent shall comply with the provisions of the Technical Specification for Application of Concrete Admixtures GB 50119 - 2003; after adding the expansive agent, the free expansion of the cement slurry without restraint shall be less than 10%;

[0064] For the mixing of the cement slurry, water shall be first added to the mixer, and then cement shall be put in; after sufficient mixing, the admixture shall be added; the water content in the admixture shall be included in the water-cement ratio. The mixing shall be carried out for at least 2 minutes until a uniform consistency is achieved, and the consistency shall be controlled between 14 - 18s.

[0065] b) Grouting: Duct grouting shall be carried out immediately after the tensioning of the prestressed steel tendons is completed, generally not exceeding 14 days; the continuous time from the modulation of the cement slurry to its injection into the duct shall generally not exceed 30 - 45 minutes.

[0066] c) End sealing: After the duct is grouted, the slurry on the beam end etc. shall be cleaned, the concrete at the beam end face shall be roughened, the end reinforcement mesh shall be tied, the end formwork shall be assembled, fixed after formwork erection, and the end sealing concrete shall be poured.

[0067] 4) Bridge deck construction.

[0068] Erect the T-beams, and carry out the construction of the bridge deck paving concrete after the erection of the T-beams is completed.

[0069] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is customarily placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the present invention.

[0070] In addition, when the terms "horizontal" and "vertical" appear in the description of the present invention, it does not mean that the components are required to be absolutely horizontal or hanging vertically, but they can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and it does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0071] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, if the terms "set", "installed", "connected", "connected" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0072] The above is only a preferred embodiment of the present invention, and does not impose any formal limitations on the present invention. Any simple modifications and equivalent changes made to the above embodiments based on the technical essence of the present invention all fall within the protection scope of the present invention.

Claims

1. A construction method for an assembled traffic bridge at a flood discharge opening, characterized in that, The construction method of curved bridge straight construction includes the following steps: 1) Construction of abutments and piers; abutment construction includes the steps of abutment foundation excavation, anchor rod construction, foundation pouring construction, abutment body pouring construction, abutment cap pouring construction and abutment backfilling; In the backfilling step of the platform, the backfilling operation is carried out in two construction periods. The first construction period is to construct the platform body to the flood season water level. During this construction period, the platform back and the surrounding area are backfilled every time a bin is poured during the platform body construction and pouring process; the second construction period is to backfill the platform back for the part of the platform body located above the flood season water level after the platform body construction is completed; in the backfilling step of the platform back, in the first construction period, the platform back is backfilled to 50cm below the bin surface elevation every time a bin is poured on the platform body; During the construction of the abutment, the part below the water level during the construction flood season is poured in multiple bins, including: foundation pouring construction, the pouring height is the height of the abutment foundation; the pouring of the abutment body is poured in multiple bins, and the pouring construction height of each bin is the same and does not exceed 1 / 3 of the overall construction height; During the foundation pouring construction and platform pouring construction, the pouring support is set up in layers. After the pouring of each bin is completed, the pouring support is removed, the back of the platform is backfilled, and the pouring support is set up on the backfilled basis, and then the pouring construction of the next bin is carried out; In the foundation pouring construction, the height of the pouring support must be greater than the height of the abutment foundation, and in the pouring construction of each bin of the abutment body, the height of the pouring support must be greater than the height of each bin; The pouring construction of the abutment adopts wooden formwork. Before installing the formwork, the formwork is assembled into a whole. During assembly, the formwork joints are staggered by no more than 1mm, and sponge strips are sandwiched between the joints. Install the overall formwork to the construction location. After the formwork is in place, use pipe racks and wood to support it, and use platform steel bars to fix it; During the compartment casting construction of the abutment body, after the construction formwork of each compartment is installed, the position of the formwork is initially adjusted according to the abutment edge line and axis line laid out on the concrete cushion or the concrete surface of the previous compartment, including the adjustment of the diagonal and verticality of the formwork. The adjustment of the diagonal of the formwork is to adjust the side formwork of the formwork to roughly coincide with the edge line of the abutment; after the initial adjustment is completed, the formwork is fine-tuned until the formwork installation meets the design requirements; 2) Cap beam construction; 3) T-beam prefabrication construction; 4) Bridge deck construction.

2. The construction method of the prefabricated traffic bridge at the flood discharge hole according to claim 1, characterized in that, After the foundation excavation is completed, the foundation anchor bars and anchor rods are placed at the locations. The foundation anchor bars and anchor rods are mortar anchor rods of a certain diameter. The anchor rod burial depth is not less than 3m, and the exposed length is not less than 1.0m. The foundation anchor bars and anchor rods are arranged in multiple rows and no less than 3 rows. The number of roots in each row is not less than 27, and the spacing between each row is not more than 1.0m.

3. The construction method of the prefabricated traffic bridge at the flood discharge opening according to claim 1, characterized in that, After the formwork is installed, supports are added to the outside of each side of the formwork to reinforce the formwork. After the formwork is processed, the concrete top elevation of the warehouse is measured and marked every 2m on each side of the formwork.

4. The construction method of the prefabricated traffic bridge at the flood discharge hole according to claim 1, characterized in that, During the pouring construction of the platform body, the concrete pouring is carried out in layers, with a layer thickness of 30-50cm, and each layer is vibrated and compacted; The vibration operation is carried out with internal vibrators. The vibration positions are controlled in a quincunx pattern, and the spacing is not greater than 1.5 times the effective vibration radius. When vibrating the upper layer, it is inserted about 5 - 10 cm into the lower layer to make the upper and lower layers of concrete closely combined. After the initial setting of the concrete in each bin, the top surface of the concrete is roughened and the surface floating slurry is removed.

5. The construction method of the prefabricated traffic bridge at the flood discharge opening according to claim 1, characterized in that, The construction is carried out in the form of slope - attached concrete combined with cable anchors under the abutment.

6. The construction method of the prefabricated traffic bridge at the flood discharge opening according to claim 1, characterized in that, The area between the approach - to - plant traffic opening and the abutment is backfilled with C25 mass concrete.

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