Key points for safety construction control of the

2022-08-24
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Key points for safe construction control of bridge and culvert works

1. Open cut foundation

(1) the method and sequence of foundation pit excavation and the installation of supporting structures shall be carried out in accordance with the provisions of the construction organization design

(2) when excavating the foundation pit, a special person should be assigned to check the safety of adjacent buildings or temporary facilities, and the inspection records should be kept. If it is affected or unsafe, safety protection measures should be taken before excavation. When the depth of the foundation pit exceeds 1.5m, a special slope or a springboard must be dug for convenience, and its width should be more than 60cm. A ladder or soft ladder should be set in the deep and narrow groove, and it is forbidden to step on the solid wall to support up and down

(3) when excavating the foundation pit, it is necessary to excavate in layers according to the specified slope gradient according to the soil, hydrology and other conditions. Local deep excavation and hole excavation are strictly prohibited. If the depth of the foundation pit exceeds 1.5m and there is no support, the slope shall be made as required

(4) during the excavation of foundation pits and pits, the pit wall slope must be checked at any time for cracks and collapse. If cracks, movement and other dangerous precursors are found on the slope, protective measures should be taken immediately

(5) excavate the foundation pit with excavators. No one is allowed to work in the pit. When people must be left to operate in the pit, the excavation machinery should be suspended

2. Safety control of bored pile foundation construction

(1) after the drilling rig is in place, a comprehensive inspection should be carried out on the drilling rig and its supporting equipment, such as whether the winch, steel wire rope, drill bit, mud pump, water pump and electrical equipment are perfect and normal. The installation of the drilling rig must be stable and firm, and the drill frame should be equipped with diagonal bracing or cable wind rope

(2) during the operation of all kinds of drilling rigs, they should be operated by the operators designated by the machine or the person in charge of machine management. Others should not board because of the close connection between China's extruder products and strategic new industries. The operator shall not leave the post without authorization during the shift

(3) each time when replacing drill pipes and drill bits, it should be fast and fast to ensure continuous and reliable

(4) when using impact drilling, the damage of the selected drill cone, winch and steel wire rope must be replaced immediately when the broken wire has exceeded 5%, and the number of clips connected between the steel wire rope and the drill bit should be installed according to the same strength

(5) the steel wire ropes on the winch sleeve should be arranged neatly. When the winch is operating on the steel wire rope, it is strictly forbidden for the operator to cross it. The steel wire ropes on the winch drum should not be completely placed, and at least 3 circles should be reserved

(6) during the drilling process, a special person must be assigned to maintain the height of the water level in the hole and the consistency of the slurry according to the specified indicators. To prevent hole collapse

(7) when the drilling rig stops drilling, the drill bit must be raised out of the hole and placed on the drill frame. It is strictly forbidden to leave the drill bit in the hole for too long

(8) during drilling, when a fault needs to be eliminated, it is strictly forbidden for operators to go down the hole to deal with the fault

(9) the mud pit should be equipped with obvious warning signs and protective fences. After the pile foundation construction is completed, the mud should be cleaned in time to prevent environmental pollution, and the mud pit should be backfilled

3. Construction of dug pile foundation

(1) dug cast-in-place piles should be excavated and built in dense soil layers or rock layers without water or little water according to the design. When the dug hole is deep or there is water seepage, measures such as hole wall support, drainage and precipitation must be taken to strictly prevent hole collapse

(2) the top of the head of the excavation personnel in the hole should be set with a protective cover, and the excavation personnel should work under the protective cover when the borrow crane head rises and falls. In the two adjacent holes, when pouring concrete in one hole, the excavation personnel of the other hole shall stop the operation and withdraw from the well hole

(3) before digging the hole, the air in the hole should be discharged and replaced with a blower. Ventilation measures shall be taken when the content of carbon dioxide exceeds 0.3%

(4) if the manual excavation is more than 10m deep, mechanical ventilation should be adopted, and there must be sufficient support facilities and standing safety ladders to ensure safety

(5) when concrete retaining wall is used for manual pile excavation, the retaining wall shall be poured immediately every 1m of excavation depth, and the thickness of the retaining wall shall not be less than 10cm

(6) the excavated earthwork should be transported out as soon as possible. If it cannot be transported away temporarily, it should be stacked 1m away from the orifice edge, and the stacking height should not exceed 1m. When there are people working in the hole, there should be no motor vehicles driving or parking within 3M

4. Pier and abutment works

(1) cast pier and abutment concrete in place. Before construction, scaffolds and working platforms must be erected. When the height of the pier body is m, railings and escalators should be set outside the platform; When it is more than 10m, stern has been developing polymers for the friction and wear of automotive systems in the past five years, and safety should be added. Construction personnel shall fasten safety belts for operation

(2) after the formwork is in place, its position should be fixed immediately with braces to prevent the formwork from falling and hitting people

(3) in the process of erecting the pier body formwork of the pier, the operator installing the formwork must fasten the safety belt and tie it to a firm place. The tie rod through the formwork should echo inside and outside

(4) before the hoisting of the overall formwork, the formwork should be firmly connected, and the internal support rod and stirrup should be tightened; The lifting point should be correct and firm. When lifting, fasten the sliding rope and follow the signal command. Overload is not allowed

(5) when pouring concrete, it is not allowed to pour it directly with a large tank funnel to prevent impact on the formwork. During vibration, the jacking rod, reinforcement and formwork shall not be vibrated. When lifting the formwork, vibration is not allowed

(6) sufficient lighting shall be provided for night construction, and fixed lighting facilities shall be set up for personnel up and down and on the transportation aisle. Lighting equipment should use a safe voltage below 36V

(7) in order to prevent the formwork from tilting and twisting, the lifting speed is controlled at cm/h

(8) the installation of the bearing should be carried out according to the design. Wipe the surface stains of the bearing, apply alcohol or acetone, and it is strictly forbidden to replace it with gasoline, kerosene, etc

5. Superstructure engineering

(1) key points for safety control of prefabricated component installation

the layout of Prefabrication Yard should be reasonable, and the stacking of prefabricated beams should be standardized and stable. The construction of prefabricated installation components should not be carried out at night, and workers are prohibited from working fatigue. During the installation and hoisting of simply supported beams, the staff on the pier top shall leave temporarily. It is forbidden for the staff to stand on the pier cap top to command or work in parallel

① for the installation of fabricated components (beams and plates), an installation scheme should be formulated and a unified command system should be established. For the operation projects with great construction difficulty and danger, the construction technology, command and operation personnel shall be organized for training. All lifting equipment shall comply with the national safety regulations on special equipment and be strictly managed. In actual operation, the following regulations shall be strictly implemented

1) before hoisting, it is necessary to check whether the safety technical measures and safety protection facilities are complete, and whether the setting of machines and tools, the weight, length of components and the position of hoisting points meet the design requirements. It is strictly forbidden to carry out construction without preparation

2) scaffolds, working platforms, protective railings, upper and lower stairways and safety must be complete for construction

3) check the damage degree of the old steel wire rope before use. The broken steel wire in each pitch shall not exceed 5%. New steel wire ropes should be used for the hoisting of large components and reconstruction parts, and they should also be inspected before use

4) for major hoisting operations, trial hoisting should be carried out first. Carry out observation in stages according to the designed lifting weight, and carry out formal lifting operation only after it is confirmed to be correct. During construction, the main leaders and full-time and part-time safety officers on the site should personally command and supervise

5) in case of severe weather such as strong wind and thunderstorm, the operation shall be stopped. It is strictly prohibited for other construction personnel to engage in parallel operations of other projects under the boom

② according to the size and quality of hoisting components, select appropriate hoisting methods and machines and tools, and do not overload hoisting

③ the center line of the hook must pass through the center of gravity of the lifting body, and it is strictly forbidden to tilt the lifting and unloading components. When hoisting eccentric components, lifting appliances with adjustable eccentricity shall be used for hoisting. The installed components must rise and fall smoothly, be in place accurately, and be close to the support

④ when lifting large and protruding edge components, a cushion should be set at the corner where the steel wire rope contacts the component

⑤ when installing components of single guide beam and pier top gantry, the following provisions should be followed:

1) when assembling two, each node should be firmly connected. When advancing in the middle of the bridge span, the cantilever part should not exceed 1/3 of the total length of the assembled guide beam

2) the guide wheel support passed by the pier top or temporary pier top guide beam must be firm and reliable. When the guide beam approaches the guide wheel, it should enter the guide wheel in a gradual way. After the guide beam is pushed in place, jack it up and place it on a stable wooden pier

3) the track on the guide beam must be laid in parallel and equidistant. When using rails of different specifications, its joints should be properly handled without staggering

4) when the gantry on the pier top is transported with brackets, both ends of the brackets should be balanced and stable, and the speed should be slow. After the gantry is placed, it should be immediately connected with the embedded parts on the pier top, and the cable wind rope should be tied

5) after the components are hoisted and loaded in the Prefabrication Yard, when they are towed to the guide beam, the traveling speed shall not be greater than 5m/min. After reaching the installation position, the traveling wheel of the flat car shall be wedged tightly with a wooden wedge

6) after the component is lifted and moved in place, support and skid should be added to maintain the stability of the component

7) brake sleepers shall be set at both ends of the gantry top traverse track

⑥ when Jack is used in the Prefabrication Yard to jack up the components for loading and install the components of double guide beam and truss beam, the following provisions should be observed:

1) before using the jack, the bearing test should be done. The lifting tonnage shall not be less than 1.2 times the test stroke of the jacking member: the performance and requirements of the flexible packaging film to be tested, and the height of the jack's primary top length shall be 1/3 of the piston stroke

2) safety skids should be added or pulled out at any time when lifting the jack, and the distance between the bottom of the component and the safety skid should be controlled within 5cm

3) when the member enters the beam falling or other loading tools move horizontally in place, the balance and stability of the member during beam falling shall be maintained

4) when jacking large tonnage components of box girder, support must be added at both ends of the beam. Both ends of the component shall not be jacked up or dropped at the same time; When one end is jacked up, the other end should be firmly supported

5) the sliding equipment of the precast yard and pier top loading members should have sufficient strength and stability, and the force should be applied evenly when pulling (or pushing) the members to slide

6) keep the two guide beams at the same speed when moving forward. All posts should work carefully, follow the instructions of special personnel, and deal with problems in a timely manner

7) before and after the double guide beam enters the pier top guide wheel support, the same measures as the single guide beam should be taken

⑦ when installing components, the bridge erecting machine shall comply with the following provisions:

1) the assembly of bridge erecting unit, the balance and stability in cantilever traction and the allocation of machines and tools shall be carried out according to the design requirements

2) after the bridge erecting machine is in place, in order to maintain the stability of the front and rear fulcrum, square wood support pads shall be used. The front and rear fulcrum points shall also be sealed and fixed on both sides of the pier top with cable wind rope

3) when the components move vertically and horizontally on the bridge, they should be carried out smoothly, and the winch operator should act in coordination according to the command signal

4) before the side beam lifted by the full width erecting machine is in place, the pier top operators should temporarily avoid it

5) for the components that cannot be moved in place at one time, the operator should prepare the slide plate, beam drop frame, etc., and enter the operation point to push (or pull) the components horizontally after the components fall

⑧ when installing components on the gantry crossing pier, corresponding safety measures should be taken according to the height and span of the gantry to ensure that the components are hoisted and transversed

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