First, the construction preparation
(1) operating conditions
1. The stratum, geological structure, engineering geology and hydrological conditions of the whole line have been surveyed and designed.
Unit acceptance.
2. Complete foundation lofting and foundation treatment.
3. According to the requirements of design specifications, check the concrete mixture ratio and complete the concrete mixture ratio. raw material
After the second interview, technical disclosure, platform scale calibration and inspection, prepare for concrete test.
(2) Site preparation
1. In order to make the foundation strength meet the stress requirements, be uniform and overcome uneven settlement, the undisturbed soil should be removed first.
After rolling, except for 40cm, backfill 3: 7 lime soil (30cm thick) and press the road with bulldozer vibration.
Mechanical compaction, its compaction strength reached more than 95%, and maintenance for 7 days.
2.3: 7 After the lime-soil base construction is completed, pave 10cm~20cm thick gravel for leveling and compaction.
Mechanical rolling of pavement is smooth and dense. The bearing capacity of the treated foundation can reach above 80kPa.
3. Put 2% drainage slope along the center of the bridge, and dig 80cm wide and 40cm deep on both sides of the support.
Drainage ditch, rainwater and sanitary water shall be discharged in time to prevent the foundation from soaking.
(3) Raw materials and mechanical equipment
1. The grades and specifications of various raw materials such as steel bars, cement, aggregates and additives must meet the design requirements.
The quality conforms to the current standards.
2. All kinds of equipment and materials for concrete, steel bars, formwork and prestressed construction shall have quality certificates.
Two. quality requirements
(1) Scaffolds and templates
1. Installation of support and formwork
The supporting structure should meet the adjustment requirements of riser elevation. Template should be installed according to the design elevation and construction camber.
Table 2~ 1: allowable deviation of formwork, bracket and arch installation
Allowable deviation of the project (mm)
Foundation formwork elevation 15
Columns, walls and beams 10
10 pier
Internal dimensions of formwork for all members of superstructure+5,0
Cardinal number 30
Pier and abutment 20
sequential
Axis offset foundation 15
Column or wall 8
Beam 10
10 pier
Elevation of bearing surface of precast member +2, -5
Surface height difference between two adjacent plates of template 2
Template surface leveling 5
The center line position of embedded parts ` 3
Center line position of reserved hole 10
Internal dimension of reserved tunnel section+10/0,0
11000 or 30, the span of the plane position of the longitudinal axis of the support and arch.
Arch bending elevation +20,-10.
2. Removal of supports and templates
(1). The formwork shall be dismantled according to the design order, following the order of supporting before dismantling, supporting before dismantling, and throwing is strictly prohibited during dismantling.
(2) Unloading bracket shall be carried out according to the proposed unloading procedure, and unloaded in several cycles. The unloading amount should be small at first, and then one by one.
Gradually increase. In the vertical direction, it should be balanced and unloaded simultaneously in the horizontal direction.
(3) Non-load-bearing side formwork shall ensure that the strength of concrete can ensure that its surface and edges and corners are not affected by formwork removal.
Damage, or when the compressive strength of concrete is greater than 2.5MPa, can be removed.
(4) The load-bearing formwork and support of reinforced concrete structure should be able to bear the dead weight and other possibilities in concrete strength.
Only when the load is superimposed can it be removed.
(2) Processing and installation of steel bars
Table 2~2: Allowable deviation of processed steel bars
Allowable deviation of the project (mm)
The total length of steel bars processed along the length direction is 10.
The size of each part of the bending steel bar is 20.
The size of stirrups and spiral bars is 5.
Table 2~3: Allowable deviation of welded mesh and welded skeleton
Allowable deviation of project (mm) Allowable deviation of project (mm)
Length and width of net/width and height of skeleton of 10/0 5
Grid size 10 skeleton length 10
Grid 10 diagonal difference of stirrup spacing 0, -20
Table 2~4: Lap length of binding joint of tensile reinforcement
Strength grade of steel reinforced concrete.
C20 C25 is higher than C25.
Level 1 rebar 35d, 30d and 25d
Crescent HRB335 brand rebar 45d 40d 35d
HRB400 brand rebar 55d 50d 45d
Table 2~5: Allowable deviation of rebar position
Allowable deviation of the project (mm)
The reinforcement spacing of more than two rows of reinforcement is plus or minus 5.
The spacing between steel bars in the same row of beam, slab and arch rib is 10.
Foundation, pier, abutment and column 10
Rebar bending starting point position 20
The spacing between stirrups and transverse reinforcement is 20.
Location of welding center line of embedded parts 5
The horizontal height difference is plus or minus 3
Thickness of protective layer of pier foundation 10
Column, beam and arch rib 5
Plate 3
(3) Transportation, pouring and curing of concrete
1. Delivery of concrete
(1). The transportation of concrete mixture should be as short as possible, with less transshipment, so as to shorten the transportation time and meet the pouring speed.
Requirements, and maintain the plasticity of concrete.
(2) The concrete shall not be separated during transportation.
(3) After the concrete is transported to the pouring site, it should generally be placed directly at the pouring site without moving. The pouring height shall not exceed 1.5m. If it exceeds1.5m, formwork shall be poured in series or in layers.
Concrete strength grade, the temperature is not higher than 25℃, and the temperature is higher than 25℃
≤C30 2 10 180
> C30 180 150
Table 2~6: All allowable time for concrete transportation, pouring and intermission (minutes)
2. Concrete pouring
Concrete should be poured in layers according to a certain thickness, sequence and direction, and the upper concrete should be poured before the lower concrete is initially set or can be reshaped. When the upper and lower layers are poured at the same time, the pouring distance between the upper and lower layers should be kept above1.5m. When pouring concrete on the inclined plane, it should be expanded and raised from the lower part step by step, and horizontal stratification should be maintained.
Thickness of pouring layer by vibro-compaction method (mm)
With the plug-in vibrator 300
With the attached vibrator 300
When using surface vibrators without reinforcement or with sparse reinforcement, 250
When steel bars are dense, 150
At 200, manually vibrate without reinforcement or sparse reinforcement.
When steel bars are dense, 150
3. Maintenance of concrete
(1). For the concrete centrally maintained on the construction site, a specific maintenance plan should be put forward according to the construction object, environment, cement varieties, additives and requirements for concrete performance, and the specified maintenance system should be strictly implemented.
(2) After the concrete pouring is completed, it should be covered and watered as soon as possible after the slurry is collected. For hard concrete, concrete poured in hot weather, bridge deck and other large-area exposed concrete, if possible, a shed cover can be added immediately after pouring, and the slurry can be covered with water for curing. The covering shall not damage or pollute the concrete surface.
(3)。 Generally, the water curing time of concrete is 7d, which can be extended or shortened according to the humidity, temperature, cement varieties and additives of the air. The number of times of sprinkling water every day is to keep the concrete surface in a wet state.
(4). Prestressed construction
Control the number of category check items.
Harness and
Steel strand bundle: each bundle 1 broken or slippery wire.
1 Broken or slippery wire of each strand.
The total number of broken wires in each section shall not exceed 1% of the total number of steel wires in that section.
Rebar fracture or single rebar sliding is not allowed.
Table 2~8: Post-tensioned Prestressed Bar Slip and Broken Wire Limit
Allowable deviation of the project (mm)
Pipeline coordinate beam length direction 30
Beam height direction 10
Distance between pipelines in the same row 10
Upper and lower floors 10
Table 2~9: Allowable Deviation of Post-tensioned Prestressed Bar Fabrication and Installation
Three. process flow
(1). Steel binding technology
Check the semi-finished steel bar → draw the steel bar position line → transport the steel bar to the use part → hoist the steel bar skeleton in place →
Binding reinforcement of bottom plate and web plate → placing Ma Dengtie and cushion block → (after pouring concrete of bottom plate and web plate) binding reinforcement of top plate.
And embedded parts
(2) Scaffolding and formwork installation technology
Foundation treatment → erection of bowl buckle bracket → laying square timber and wooden wedge at the top of bracket → installing box girder bottom formwork and side formwork → adjusting the elevation of box girder bottom formwork → installing box girder top formwork and wing plate (after pouring bottom and web concrete).
(3). Concrete construction process
Operation preparation → concrete mixing → concrete transportation → concrete pouring and vibrating → maintenance.
(4) Prestressed construction process
Reserved channel → Installation of prestressed steel strand → Tension → Pipe grouting → Anchor sealing.
Four. building technology
(1). Reinforcement construction technology
1. raw materials: the surface of steel bar is clean, and the floating skin, rust, oil stain and dirt should be removed before use. Steel bars shall be straight without local bending; Rolled steel bars or bent steel bars should be straightened before use; When straightening, steel bars should not be damaged.
2. Reinforcement processing: Reinforcement processing shall be carried out in strict accordance with the design drawings, and the diameter and grade of reinforcement shall meet the requirements of the design drawings, and the reinforcement shall be free of cracks, broken wounds and nicks. The allowable deviation of processed steel bars shall meet the following requirements: the elongation of cold-drawn straightening shall not be greater than 65438 0%; The local bending after straightening is not more than 0.25 times of the bending steel bar; The forming length of a single steel bar is not more than10mm; A single stirrup (width and height) shall not exceed-3mm.
3. Reinforcement binding: According to the reinforcement spacing shown in the drawings, use Mo Dou to pop up the spacing between the main reinforcement and the distribution reinforcement. According to the design requirements, put the stressed main reinforcement first, and then put the distribution reinforcement. When binding, the intersection shall be bound firmly with double diagonal lines (crosshairs) of iron wire, and the stirrup shall be perpendicular to the main reinforcement or horizontal reinforcement. When binding, the main reinforcement should be fastened around, the intersection of stirrups and steel bars should be fastened, and the intersection of straight parts in the middle can be staggered into a plum blossom shape. The steel skeleton with binding number should have sufficient rigidity and stability, so that the position of steel bars will not change during concrete pouring. If the rigidity is not enough, the binding points should be increased or necessary vertical bars should be provided. After the steel bars are bound, plastic pads should be added to ensure the thickness of the protective layer.
4. Reinforcement lap joint: In principle, stirrup lap joint is not allowed, and horizontal reinforcement can be bound and lap joint, and the length of binding lap joint is not less than 35d. When the length of the main reinforcement is insufficient, double-sided lap welding shall be adopted, with the weld length not less than 5d, the weld width not less than 0.7 times of the diameter of the welded reinforcement, and not less than 10mm, and the weld thickness not less than 4 mm..
(2) Formwork construction technology
1. Template installation:
(1). Before construction, the rigidity and strength of the formwork shall be calculated in detail to ensure the stability of the formwork and the shape of the structure.
The exact shape and size.
(2) The members should be connected as closely as possible to reduce the deformation of the support and make the settlement meet the expected value.
(3) Template joints must be tightly closed. If there is a gap, it should be blocked tightly to prevent leakage.
(4) When the formwork is erected, the formwork shall be vertical and accurately positioned. Formwork shall be reinforced by pulling screws.
As well as formwork and wooden braces. During reinforcement, the pull screw should be tightened and the wooden brace should be firm.
(5) When the gap between formwork joints is greater than 2mm, it shall be filled with gypsum or sealed with adhesive tape. When the anchorage gap of prestressed pipeline is large, sponge foam should be used to fill it to prevent slurry leakage.
(6) After formwork installation, plane position, top elevation, node connection and vertical and horizontal stability should be considered.
Check the signature before pouring concrete. When it is found that the formwork exceeds the allowable deviation deformation value during pouring, it should be corrected in time.
2. Removal of the template
(1). Side formwork removal: Only after the concrete reaches a certain strength can it be guaranteed that its surface and edges and corners will not be damaged by formwork removal.
Demolition. Generally, it can only be dismantled when the compressive strength of concrete reaches 2.5MPa. First, dismantle the non-bearing formwork, and then dismantle the bearing part formwork, from top to bottom.
(2) Dismantle the bottom formwork: remove some horizontal tie rods and shear braces of the bracket for operation. Lower the pillar and jack it, first remove the hook bolt, then remove the bolt, then pry the template lightly with steel, or tap it lightly with a wooden pestle, remove the first piece, and then remove it piece by piece. It is forbidden to let the removed template fall freely.
(3). Concrete construction technology
1. The concrete shall be stirred in strict accordance with the approved mixture ratio, and the cement consumption of each party shall not be less than 350Kg. The concrete must have certain workability and durability, and the slump shall be between 16 cm and 18 cm when transported to the site. When pouring concrete, guide the concrete into the formwork with a pump truck conduit, and the free falling height of the concrete shall not exceed 2m.
2. The concrete shall be poured in layers and vibrated with an internal vibrator, and the thickness of each layer of concrete shall not exceed 2/3-3/4 times of the thickness of the vibrating rod. When vibrating, the vibrating rod should move up and down continuously to make the vibrating uniform. The vibrating upper concrete shall be inserted into the lower concrete by 5cm- 10cm, and the pouring of the upper concrete at the corresponding position shall be completed before the initial setting of the lower concrete. When moving the vibrator, you can use straight-line insertion or plum blossom insertion. The moving distance of the former shall not exceed 1.5 times of the vibration action radius, and the latter shall not exceed 1.75 times of the vibration action radius. In a word, when the vibrator moves, it should keep certain regularity as much as possible to prevent vibration leakage or over-vibration. In addition, the concrete should be cured at the same time. After concrete pouring is completed, cover it with plastic sheets, and sprinkle water regularly to keep the concrete surface moist. For the concrete surface covered by formwork, it should be watered and wetted frequently.
(4) Prestressed construction technology
1. When the post-tensioned prestressed box girder is constructed, firstly, a hole for inserting prestressed tendons is set on the beam. The size and position of the hole should be correct, the hole should be smooth, and the anchor pad embedded at the end should be perpendicular to the center line of the hole. The pipeline shall be fixed with positioning steel bars, so that it can be firmly placed in the design position in the formwork.
2. The machines and equipment used for prestress should be used and managed by specialized personnel, and maintained and tested regularly. Jack and pressure gauge should be matched and tested to determine the relationship curve between tension and pressure gauge. Tensioning machines and equipment should match the anchorage, and inspection and test should be carried out when entering the site.
3. When tensioning, the line of action of jack tension should coincide with the axis of prestressed reinforcement. When prestressed tendons are tensioned by stress control method, they should be checked by elongation, and the difference between actual elongation and theoretical elongation should meet the design requirements.
4. Due to the prestress, the concrete will be elastically deformed, and at the same time it will cause axial shortening and bending in the up and down direction. When the steel beam is eccentrically arranged on the longitudinal axis, it will be eccentric in the horizontal direction and bent in the opposite direction. Therefore, in the process of tensioning, unexpected cracks will appear in concrete. Therefore, when tensioning, we should fully grasp the direction and amount of elastic deformation, and strictly check whether there is any place to limit its deformation. Only after prestressing enough to bear its own weight can the support and formwork be removed.
5. Prestressed tendons can only be anchored after the tension control stress is stable. The exposed length of prestressed tendons after anchorage should not be less than 30mm, and the anchorage should be protected by end-capped concrete. After the anchorage is completed and qualified, the redundant prestressed tendons at the end can be cut. Arc welding is strictly prohibited, and grinding with a grinder is emphasized.
6. Flushing the pipeline with high-pressure water before grouting can not only wash away impurities and wet the inner wall of the pipeline, but also prevent the dry hole wall from absorbing water in the cement slurry and reduce the fluidity of the slurry. The number of grouting in the hole should be twice, so that the cement slurry can completely fill the hole. When the thick slurry is discharged from the slurry outlet, close the slurry outlet, keep the pressure not less than 0.5MPa for not less than 2 minutes, then pull out the nozzle and immediately plug it with a cork.
7. For the anchorage that needs anchoring, after grouting, the surrounding area should be washed clean and the concrete at the beam end should be chiseled, and then the steel mesh should be set to pour the anchoring concrete. The concrete strength shall not be less than 80% of the concrete strength of the member.
Verb (abbreviation for verb) building safety
(1). work high above the ground
1. When working at a height of more than 2 meters, protective facilities should be installed. If conditions do not permit, you must use a seat belt or safety net.
2. The safety helmet used in the construction site must meet the quality standards. All personnel entering the site should wear safety helmets and wear them in strict accordance with the regulations.
3. Scaffolding shall ensure that the foundation is firm, the safety platform is wide enough for people to walk (at least 60cm wide), and it is reliably connected with the fixed structure, and equipped with guardrails and walking baffles to ensure the safety of the upper and lower platforms.
4. In the case of high wind speed and bad weather, try to avoid aerial work. Special attention should be paid when handling parts in windy conditions.
(2). Objects falling
1. Tools and materials are forbidden to be placed on scaffolding in aerial work area. In order to prevent objects from falling, there should be a baffle and a small enough protective net.
2. When working at high altitude, avoid working at low altitude below it. If the work must be carried out in a dangerous area, only important work and key personnel are allowed to enter.
3. Dangerous areas should have obvious warning signs.
(3). Lifting operation
1. Every hoisting operation must have a detailed plan. After the crane is installed, it must be inspected and accepted. Hooks must be equipped with safety devices. Before using the derrick, you must try to hoist it. Wear and broken wire of wire rope shall not exceed the standard. The lifting point must be accurate. Lifting personnel must be trained and hold a work permit.
2. On-site commanders and hoisting personnel should wear brightly colored work clothes, be vigilant and be ready to deal with emergencies. In order to ensure the safety of the hoisting site, obvious warning signs should be set up, and non-working personnel are prohibited from entering.
(4). Thermal prevention
1. Conduct fire fighting training for employees, clarify emergency procedures, install monitoring and alarm systems, and master correct fire fighting methods.
2. In order to effectively prevent fire, it should be stipulated that smoking is strictly prohibited in inflammable and explosive places and fire-forbidden areas, and electrical appliances and wires are not allowed to be installed without authorization. It is forbidden to use unproductive electric heaters, kerosene stoves and other bare appliances without authorization.
3. Correct selection, installation, use and maintenance of electrical systems and equipment. The system should be well maintained, and full-time personnel should be responsible for regular inspection.
4. Set up eye-catching signs such as "Beware of electric shock" in the power consumption area.
Environmental protection of intransitive verbs
In order to strengthen the environmental protection work of highway construction and reduce the environmental pollution caused by highway construction, it is necessary to cut
Do a good job in prevention and control measures, protect natural resources and improve the ecological environment and people's living environment. In the process of construction, in addition to strictly observing the technical specifications issued by the Ministry, environmental protection regulations for yard management and design instructions, the following specific construction measures should also be implemented:
1. Clean the transport vehicles entering and leaving the county and township roads, ensure the roads are clean and tidy, and cover the sails.
Cloth, prevent scattering, if it happens, send someone to clean it up in time.
2. Stack building materials such as sand and stone according to the design requirements. Set up a baffle for transporting concrete and sand, so as to
Don't throw or scatter.
3. The oil depot is set in a safe zone, equipped with full-time personnel on duty and firefighters, with complete safety facilities.
4. Discharge waste oil, waste water and waste residue at designated places to avoid air and water pollution. Do not damage farmland, water conservancy construction and transportation facilities at will, and pay attention to the interests of the masses.
5. Pay attention to the frequent watering maintenance of the construction access road to prevent dust and environmental pollution.
6. After work, all kinds of construction machinery and vehicles should be neatly parked in the designated parking lot.
7. Pay attention to workers' health and beautify the living environment.
Seven. Quality problems that should be paid attention to
(1). Quality problems that should be paid attention to in reinforcement engineering
1. Before pouring concrete, check whether the rebar position is accurate. Welding or binding joints of reinforced bars shall be arranged in places with small internal forces and staggered from each other. For binding joints, the distance between the two joints should not be less than 1.3 times the overlapping length. In the joint length section, there should be no two joints for the same reinforcement.
2. The concrete protective layer at the joints of steel bars shall meet the design requirements, and shall not be less than 15mm, and the horizontal clear distance between joints shall not be less than 25mm.
3. A cushion block should be set between the steel bar and the formwork, and the cushion block should be firmly bound with the steel bar and staggered with each other. Short reinforcement pads should be placed between multiple layers of reinforcement, and there is no welded reinforcement skeleton to ensure accurate position. The thickness of reinforced concrete protective layer should meet the design requirements.
4. When the skeleton is welded and spliced, the position of the skeleton should be strictly controlled by the template. The welding sequence of the skeleton should be from the middle of the skeleton to both sides, symmetrically to both ends, welding the lower part first, then welding the upper part. Each weld should survive once, and adjacent welds should be welded symmetrically in different regions, and continuous welding in the same direction is not allowed.
(2). Quality problems that should be paid attention to in formwork engineering
1. Formwork and reinforcement installation shall be coordinated. Formwork that interferes with steel bar binding shall be installed after steel bar installation. Formwork shall not be connected with scaffold to avoid deformation of formwork.
2. Reuse the template should always keep its surface smooth, accurate shape, no leakage, and have enough strength and stiffness.
3. The surface of the wooden pattern in contact with the concrete should be smooth, and the wooden pattern that has been reused for many times should be nailed with thin iron sheets on the inside. The joints of wooden patterns can be made into flat joints, lap joints or tongue-and-groove joints. When using flat seam, measures should be taken to prevent slurry leakage. The corners of the wooden model should be inlaid or beveled.
4. The surfaces of interconnected formwork shall be aligned, and the connecting screws shall not be tightened in place at one time. Check the template line type as a whole, adjust it in time if there is any deviation, and then lock the connecting screws to fix the support rods.
5. The elevation of bottom plate and wing plate shall be set out in strict accordance with the design elevation.
6. If there is height difference after flat-fell seam, it is not allowed to cut off the higher one, but a thin one should be used between the lower plate and the rib.
Chip buffer pad
(3). Quality problems to be paid attention to in concrete engineering
1. Honeycomb: the proportion of concrete is inaccurate, and the measurement of sand and gravel is wrong; Short stirring time and poor workability; Construction vibration is not dense, vibration leakage; The reinforcement is too dense, the concrete slump is too small or the stones are too large, and there is no delamination or slurry leakage.
2. Pockmarked surface and interlayer: the vibration is not compact, and the air bubbles are not fully discharged, especially when the box girder is poured, it takes a long time to wait for the concrete, and the vibrating rod is not inserted deep enough during vibration, resulting in poor contact between the upper and lower layers. When the formwork is removed too early or the formwork is not wet enough, the concrete on the surface of the component is easy to stick to the formwork, resulting in peeling of the pits.
3. Spots: the template is not cleaned cleanly, and the template has rust spots; Poor gravel grading and too much gravel make the cement slurry unable to completely wrap the gravel; The use of cement slurry pad will also cause local concrete color inconsistency.
4. Exposed reinforcement: the displacement and spacing of the reinforcement pad are too large, which causes the reinforcement to cling to the template. The bottom of the plate is not compacted by vibration, and steel bars may be exposed.
5. Holes: the concrete in the dense part of steel bars is stuck, and the upper concrete continues to be poured, but it is not tamped.
(4). Quality problems that should be paid attention to in prestressed engineering.
1. Broken wire, uneven or severely corroded steel strand material; The anchor ring mouth overlaps when splitting wires; During operation, the hole, anchor ring and jack are misaligned, resulting in the steel wire being centered, uneven stress and concentrated stress on individual steel wires; The oil pressure gauge is out of order and the tension is too large; Jack is not calibrated as required.
2. Slip wire: there are inclusions between the taper hole of the general anchor ring and the clip; Ribs and jack chucks are greasy; There are residues such as concrete at the horn mouth of anchor pad; The anchorage deviates from the stop of the anchor plate; There are some problems in the quality of anchorage, which are caused by uneven hardness. Excessive oil return and inconsistent rib thickness are also one of the factors that cause slippage.
3. Pipe blockage: The pipeline is poorly sealed and the joints are improperly wrapped, so that the cement slurry enters the tunnel during concrete pouring, causing pipe blockage, which makes it impossible to stretch the prestressed tendons, and the tunnel grouting is not smooth or even impossible.