What are the seasonal and typhoon flood season construction arrangements for bridge projects?

Seasonal and typhoon and flood season construction arrangements for bridge projects

This project is limited by the construction period. Construction requires two winters and one rainy season. The specific construction arrangements under special climate conditions are as follows :

1 Winter construction arrangements

The construction period of this contract period is 14 months, and the entire project has gone through two winters. During winter construction, various construction preparations must be made in advance and reliable technical assurance measures must be taken. The main contents are as follows:

1.1 Construction preparations

⑴ Prepare winter plans and construction Organizational plan;

⑵ Take anti-snow, anti-freeze and other measures for various facilities and materials in advance;

⑶ Special construction process requirements and safety measures should be formulated for cold drawing and tensioning of steel bars;

⑷ Trial the concrete mix ratio for winter construction in advance;

⑸ Develop safety measures such as fire protection, anti-freeze, and gas poisoning prevention for winter construction;

⑹ Right Employees and migrant workers should conduct technical briefings on winter construction in advance.

1.2 Construction methods and technical measures

1.2.1 Winter construction of steel bars and prestressed steel bars

⑴ Steel bar welding should be carried out indoors as much as possible. When the wind strength exceeds Level 4, wind blocking measures should be taken. When the ambient temperature is lower than -20°C, the welding quality cannot be guaranteed and the welding operation must be stopped.

⑵ The cold drawing equipment, prestressed tensioning equipment and instrument working fluid of steel bars should be selected according to the actual ambient temperature during use, and should be calibrated under the ambient temperature conditions during use.

⑶ Grouting of prestressed concrete channels should be carried out at normal temperature.

1.2.2 Winter construction of concrete

⑴ Technical requirements for concrete preparation and mixing

① Portland cement and ordinary Portland cement should be given priority. The water-cement ratio should not be greater than 0.5.

②The mix ratio design of concrete in winter should be comprehensively considered based on the concrete pouring strength, transportation method, etc. The dosage of admixtures must be implemented in accordance with specifications.

③The temperature of the various materials used to make concrete should meet the temperature required for the concrete mixture to be mixed and synthesized (the exit temperature of the concrete mixture should not be lower than 10°C, and the mold entry temperature should not be lower than 5℃). First consider heating the mixing water. If it still cannot meet the needs, then consider heating the aggregate. Cement can only be used for insulation, not heating. The temperature at which various materials need to be heated should be calculated and determined based on the "Thermal Calculation Formula for Winter Construction" in the specification, but shall not exceed the maximum temperatures stipulated in the specification.

④ To ensure the workability and fluidity of the concrete, the mixing time can be extended, generally 50% longer than at normal temperature.

⑵Technical requirements for concrete transportation and pouring

①Concrete transportation time should be shortened as much as possible, and appropriate insulation measures should be taken for containers transporting concrete. Wrap and insulate the concrete delivery pump pipe.

② Before pouring concrete, the ice, snow and dirt on the formwork and steel bars should be removed.

③ When constructing joint concrete in winter, the joint surface should be heated to a temperature above 5℃ before the new concrete is poured. After the pouring is completed, measures should be taken to keep the concrete joint surface at a positive temperature until the new concrete is poured. The concrete is poured to obtain the specified frost resistance.

1.2.3 Technical requirements for concrete maintenance

The concrete maintenance method should be calculated and determined according to the "winter construction thermal calculation formula" in the technical and economic comparison and specifications. The maintenance method should be based on various factors such as the temperature on site and the surface coefficient of the structure. Methods such as heat storage, steam heating, greenhouse heating or electric heating can be used to ensure that the concrete structure is not damaged by freezing. This project plans to use the following methods for winter concrete maintenance:

① The exposed surface of the concrete is covered with tape and straw bags, and watering and maintenance are not allowed under negative temperature conditions.

② The temperature in the initial stage of concrete curing shall not be lower than the temperature specified by the antifreeze. When the specified temperature is not reached and the concrete strength is less than 3.5Mpa, insulation measures must be taken to ensure that the concrete temperature is not lower than Antifreeze specified temperature.

1.2.4 Concrete formwork removal

⑴ Must meet the requirements for formwork removal strength of concrete at normal temperatures, and at the same time meet the requirements for frost resistance:

Side The formwork can only be removed when the concrete strength reaches above 2.5Mpa and its surface and edges are not damaged by formwork removal. The bottom formwork should be removed only when the concrete strength reaches 100% of the concrete design strength.

⑵ The temperature difference between the concrete and the environment shall not be greater than 15℃. When the temperature difference is above 10℃ but below 15℃, cover the concrete surface immediately after removing the formwork, such as covering with straw bags and colored tape. .

1.2.5 Winter construction of bored piles

⑴ The winter construction of bored pile concrete is mainly to ensure that the concrete does not freeze during pouring and can be poured smoothly.

⑵ When the pile head is exposed to the water surface (or the ground) or is not exposed to the water surface (or the ground), but is within the freezing range, the pile head concrete should be covered with insulation and cured.

(3) The temperature of the concrete mixture during pouring is required to be no less than 5°C; antifreeze and antifreeze are not allowed to be mixed into the concrete.

1.2.6 Quality Inspection

Conduct strict inspections on all winter construction projects in accordance with the winter construction quality inspection methods required by the specifications to eliminate hidden project quality hazards. In addition, the following requirements must be met:

⑴ During the mixing and pouring of concrete, measure the temperature of water and coarse and fine aggregate when they are loaded into the mixer, the mixing temperature of concrete, the pouring temperature and the ambient temperature. Test at least 4 times per work shift. When using low-temperature early-strengthening concrete or using thermal storage method to maintain concrete, testing should be carried out at any time within 3 days after pouring.

⑵ In addition to making standard maintenance specimens for winter construction concrete in accordance with regulations, construction inspection specimens are also made according to the needs of building maintenance, formwork removal and load bearing to ascertain the development of strength. The maintenance of construction inspection specimens should be the same as that of buildings.

1.3 Measures for cold protection, antifreeze, fire prevention and anti-skid work of mechanical equipment in winter

⑴ Carry out comprehensive repairs and maintenance on all mechanical equipment before entering winter, do a good job in oil and water management, and combine For seasonal maintenance of mechanical equipment, replace the corresponding brand of lubricating oil in a timely manner; for mechanical equipment that uses antifreeze, ensure that the antifreeze meets local antifreeze requirements; for mechanical equipment that does not use antifreeze, appropriate antifreeze measures must be taken (discharge cooling water after shutdown or Entering the greenhouse workshop)

⑵ The fuel used by various vehicles should be selected according to the ambient temperature. When starting a cold vehicle, it should first run at a low speed for a certain distance and then gradually increase the vehicle speed.

⑶ Before starting the engine of a vehicle in winter, it is strictly forbidden to use an open flame to heat the existing fuel system to prevent fire.

⑷ When driving in ice and snow, the car must be equipped with anti-skid chains; the driver should check whether the vehicle's braking device is in good condition before getting out of the car. Do not get out of the car if it does not meet the requirements. In case of strong winds of level 6 or above, Operation will be stopped in bad weather conditions such as heavy snow and fog.

⑸ Strictly implement the fixed machine and fixed personnel system. Machinery custodians must stick to their posts, take good care of the equipment, and make corresponding records.

1.4 Other precautions for winter construction

⑴ When working at heights, take anti-slip measures for the steel structure and take reliable wind protection measures.

⑵ When welding steel structures during winter construction, corresponding welding processes should be adopted to ensure welding quality.

⑶ During winter construction, the heat preservation and maintenance of mechanical equipment should be strengthened to ensure the normal operation of the equipment.

⑷Construction should be stopped in strong winds, heavy snow, and foggy days.

⑸ During winter construction, pay attention to the implementation of the "five prevention" work in winter.

2 Rainy season construction arrangements

The construction period of this contract period is 14 months. The entire project has gone through one rainy season, which will have a greater impact on the construction of the project. Therefore, various construction preparations must be made in advance. And take reliable technical assurance measures. The main contents are as follows:

2.1 Construction preparations

⑴ Prepare rainy season plans and construction organization plans;

⑵ Formulate safety measures for water and high-altitude operations during rainy season construction Measures;

⑶ Prepare flood control materials, machinery and necessary rain-shielding facilities for construction during rainy periods.

(4) Keep in regular contact with the local meteorological department, obtain meteorological data at any time, grasp the annual, monthly and daily rainfall trends, arrange construction reasonably, and try to avoid construction during bad weather.

⑸ Provide technical explanations for rainy season construction to employees and migrant workers in advance.

2.2 Construction methods and technical measures

⑴ Set up a flood prevention and anti-corruption leading group in the project department, with the project department manager as the team leader. Each work section has established a flood control and anti-corruption team, headed by the head of each section, and obeys the unified dispatch of the flood control and anti-corruption leading group. The flood control and anti-information team of the project department obeys the unified dispatch of the local government and Zhenlian Road Headquarters.

⑵ Engineering materials, especially cement and steel bars, should be waterproof and moisture-proof. Bulk cement uses cement tanks, and bagged cement and admixtures are located in a cement warehouse with a brick structure. The floor of the warehouse is a concrete structure and is at least 20cm higher than the outdoor ground. Outdoor bagged cement, admixtures, etc. should be used as soon as possible, and those that are not used for a long time should be transferred to the warehouse for stacking.

⑶The formwork, steel bars, etc. are isolated from the ground with sleepers, and covered with tarpaulins when it rains. After rain, the silt and debris on the formwork and steel bars should be removed before pouring concrete.

⑷ Before pouring concrete, check the moisture content of sand and gravel in time to adjust the mix ratio. Set up a canopy when it rains during pouring to prevent rainwater from washing away the concrete.

⑸ During construction in the rainy season, water retaining banks should be set up during foundation pit excavation to prevent ground water from flowing in. There is a water collection well in the foundation pit, equipped with sufficient water pumps, and water connection measures are installed in the ramp. After the foundation pit is dug, concrete or cushioning should be poured in time to prevent it from being soaked by water.

⑹ Strengthen the observation of subsidence in areas with poor foundations.

⑺Lightning protection measures should be installed in minefields, and high-rise structures should have lightning protection designs. Typhoon prevention measures should be considered in coastal areas.

⑻ Non-motorized construction machinery and equipment should be elevated during the rainy season to prevent moisture. Electrical equipment used in the open air must have reliable anti-leakage measures (such as adding leakage protectors, etc.).

⑼ During the rainy season construction, it is necessary to strengthen the inspection, dredging or reinforcement of the drainage system inside and outside the site, and add drainage measures if necessary.

3 Typhoon prevention and flood prevention arrangements

3.1 Construction preparations

(1) Implementation organization: Establish a typhoon prevention and flood prevention leading group, led by the manager. Typhoon and flood prevention matters.

(2) Establish a rescue team: During typhoon and flood prevention periods, participate in rescue operations for national property and personnel production safety to reduce losses.

(3) Arrange on-duty duty: Special personnel should be arranged to be on duty during typhoons and flood seasons. Pay attention to the weather forecast and understand the trends of typhoons and floods.

(4) Prepare typhoon and flood prevention materials, formulate typhoon and flood prevention plans, and be prepared.

(5) Education on typhoon and flood prevention: Strengthen education and improve the awareness and participation awareness of all employees on typhoon and flood prevention.

(6) Transportation and medical support: During typhoon and flood prevention periods, there must be buses on duty to transport people and supplies, and medical personnel must be present to prepare to rescue the wounded.

3.2 Typhoon and flood prevention measures for engineering structures

(1) Emergency rescue work must be carried out at all times during typhoons, and life jackets must be worn by people on board ships and at high altitudes.

(2) Before the big waves come, temporary protection should be carried out on the length and height of the piers and the head of the beam according to the wind and wave forecast conditions.

(3) When sea conditions are good, the construction of low-water working surfaces should be accelerated to ensure the smooth progress of the overall construction.

3.3 Measures for typhoon and flood prevention for ship machinery and equipment

⑴ Implement wind shelter and anchorage for each operating ship.

⑵Implement the typhoon prevention responsibilities and action plans of each ship.

⑶ Considering the basic points of wind and typhoon prevention, during the construction of this project, a 1228kw large tugboat was specially arranged to focus on the construction of typhoon and wind burst prevention. Each construction vessel is equipped with typhoon prevention anchors. If the ship encounters a sudden wind during the construction process and cannot be towed to a sheltered port in time, it will immediately be anchored at the on-site anchorage or tied to a floating drum.

⑷ During the typhoon prevention period, no machinery and equipment may be parked at the pier.

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