The engineering quantity of a bridge and culvert is not very large, but in the preparation stage, we should also investigate the terrain, road conditions, road width, curve radius and pavement conditions to solve the possibility of trenching machinery and heavy machinery entering the site. Materials used in culverts, such as flaky and steel bars, machines and tools used, such as generators and templates, must be arranged and stored.
2. Substrate treatment
After the construction workers enter the site mechanically, the survey team will draw the edge lines of the excavated foundation pit and the top of the foundation pit. When setting out, the technical personnel of the construction team are required to set out the vertical piles, and the surveyors should specifically account for the pile location and data. After that, the foundation pit is excavated mechanically until it is 20~30cm away from the basement, and then manually excavated to the designed basement elevation, with the excavation slope of 1:2. Overexcavation and backfilling are strictly prohibited. If the backfill compaction is not enough, it may cause settlement and unnecessary waste, so the excavated earthwork will be withdrawn from the construction site, and the bottom of the foundation pit will be leveled after cleaning up the messy things to ensure that there is no silt and debris. Some testers test the bearing capacity of the pedestal. If the bearing capacity of the basement measured by penetration test can't meet the design requirements, the basement treatment scheme shall be notified to the leading laboratory in time. In the process of replacement and filling, it must be tamped and compacted, and the bearing capacity meets the design requirements.
3. Template installation
The foundation, wall and arch ring of our culvert need steel formwork. The formwork used in culvert construction is steel formwork, and the construction scaffold is bowl-shaped bracket, with ordinary scaffolding steel pipe diagonal bracing. Formwork processing conforms to the design section form and is a key point in construction, which not only affects the quality of cement concrete, but also affects the appearance of the structure. Before use, the template should be derusted and coated with release agent. Culvert formwork is made of integral steel formwork and hoisted in place as a whole. In the process of template assembly, we should carefully check and pay attention to the up-and-down order of the template and the correct position of the opening to ensure accurate size and tight joints. Thick sponge sealing strip or double-sided adhesive tape should be used at the joint of two templates, and the tie rod holes on the templates should also be sealed tightly to prevent slurry leakage. These are all easily overlooked by the construction team, and we should carefully control this. Clean up the welding slag and other sundries on the surface of the platform and foundation. According to the drawn external formwork line, before installing the column top cap reinforcement, manually cooperate with the crane to install the steel formwork in place, insert the opposite bolt into the eye hole and PVC sleeve, and the PVC sleeve is stuck in the two side panels. Do not use inserted bolts to pull the hardtop obliquely, and the steel formwork bolts should be tightened. The bolts should be staggered in front and back, and the length of the opposite bolt should be 5cm outside the transverse rib. The outside of the formwork is supported by several top bracing, and then reinforced by scaffolding to ensure the safety of construction workers and inspectors.
4. Binding of steel bars
We have steel bars on the foundation and arch ring. We should proofread the drawings carefully before binding the steel bars. When they process steel bars, we should look at the materials and check the variety, specification, quantity and size of steel bars. When binding steel bars, the spacing between steel bars should also be properly closed. When binding steel bars, add plastic cushion blocks or small cement mortar cushion blocks when binding steel bars, and put cushion blocks when binding steel bars, because the cushion blocks are put after binding. The overall weight of the steel bar is too heavy to prevent the quality from being affected by the insufficient thickness of the protective layer. Check the spacing between reinforcement and formwork. It is forbidden to zero the spacing between reinforcement and formwork, and the spacing should meet the specifications and design requirements.
check
After the formwork installation and steel binding are completed, it can't be said that it can be poured. We also need to check its geometric size, position, elevation, flat-fell seam, verticality, flatness and spacing between longitudinal and transverse ribs. Whether the release agent is evenly coated and whether the garbage under the template is cleaned up. The three inspection mode shall be implemented, and the casting can only be carried out after the inspection supervision engineer is qualified.
6. Concrete structure
Our cement concrete is uniformly mixed in the mixing station, and the mixture ratio is strictly in accordance with the requirements. Therefore, we only need to control the slump of concrete on site, and the construction personnel must wear safety helmets and do a good job in the safe construction of crane loading. Technicians must strictly monitor the construction mixture ratio of cement concrete, especially the control of water-cement ratio, because once the water-cement ratio is not well controlled by crane, it is easy to separate, resulting in poor appearance and honeycomb pits. When pouring concrete, use an internal vibrator to vibrate in layers. The free falling height of concrete pouring should be strictly controlled within 2m. Controlling the free fall height and water cement ratio to prevent concrete segregation is the key to prevent cement slurry from splashing on steel bars and formwork. Each casting height is about 30cm, and the vibrating degree is about 30cm, until the concrete surface is submerged and bubbles and blisters are no longer emitted. No leakage or repeated vibration is allowed. When the concrete is poured to the design elevation, it shall be leveled with a wooden trowel and plastered for the second time before the initial setting. Ultra-low and high plastering and shrinkage cracks in the top concrete are strictly prohibited.
7. Remove the template
The formwork removal time should be determined according to the temperature and concrete characteristics at that time, so as to prevent the formwork from being damaged due to low concrete strength or high concrete strength during formwork removal. After concrete pouring 12 hours, water and cover geotextile for initial maintenance. The formwork removal time shall not be less than 12 hour and not more than 48 hours, especially in the northern area where our project department is located. Special attention shall be paid to slow down the strength in cold winter. After the concrete is dismantled, it should be watered and covered with geotextile or sacks for maintenance, and attention should be paid to protecting the edges and surfaces of the concrete during the formwork removal process.
Any theory guiding practice comes from practice, but it should also be based on the local actual situation. In the process of culvert construction, we must constantly explore new construction methods and new technologies under the premise of ensuring quality and safety, so that our culvert construction technology can have a new development and all objectives can be better completed.
For more information about bid writing and improving the winning rate, click on the bottom customer service for free consultation.