First, the particularity of road and bridge construction mainly has the following characteristics:
1. Diversity of the project. First of all, the diversity of use functions leads to different types of engineering products. Secondly, even if the use functions are the same and the engineering types are the same, they are built in different areas, which are different because of the different geographical and environmental conditions in the construction areas.
2. The non-transferability of the project. As a product with ultimate use function, it can't be moved and can only be built where it is used.
3. Mobility of construction personnel. Workers of all types move in different parts of the project; Workers flow on various building objects in the construction site; Labor flows in different construction sites and different construction areas.
4. The project is huge, mostly in the open air, greatly influenced by natural climatic conditions, and the working conditions are difficult.
5. The construction production cycle is long. Generally speaking, a road and bridge project ranges from one year to several years. These production characteristics of construction enterprises will inevitably cause some special problems in personnel organization, arrangement and management.
Second, the problems that should be paid attention to in road and bridge construction
1. Attention should be paid to the construction quality of arch adjustment slope layer. During the construction of this layer, special attention should be paid to the specifications, gradation and mixture ratio of various materials to ensure the smoothness and compactness within the effective width of this layer, which is the basis for ensuring the quality of grassroots construction.
2. Strengthen grassroots maintenance. After the completion of grass-roots construction, use sacks for maintenance or spray asphalt emulsion for protection. If the traffic cannot be closed, the traffic of heavy vehicles shall be restricted, and the speed shall not exceed 20km/h, and attention shall be paid to the damage of other traffic facilities to the grassroots. If the car groove (pit groove) is loose, it should be repaired and compacted with the same material. It is forbidden to fill with loose granular materials.
3. In the base construction, we should strictly pay attention to the loose laying thickness, roll with the best water content, minimize the base molding, and carry out artificial renovation after initial pressing, especially to strengthen the compactness of the base edge template. For those that are not rolled in place due to special circumstances, workers' hammers and vibrating rammers should be used for layered compaction to ensure the quality of their structural layers.
4. Strictly control the leveling at the grass-roots level. Before laying the surface, use a 3m ruler to check the smoothness of the base. The sections with poor leveling and large leveling should be leveled. Before the surface layer is laid, carefully clean the base surface to ensure that the base surface is clean and tidy, and there are no loose floating materials and impurities. If there is dirt, it should be washed with pressurized water. If the local lower seal coat falls off on the surface of the base, the surface of the base at the falling place should be cleaned up, and then the prime coat asphalt or the lower seal coat should be sprinkled. Before the surface course is laid, it will be polluted by other processes. If the cement on the surface becomes hard slag, it should be removed in time to ensure the smoothness of the surface.
5. The construction quality of asphalt pavement also depends on the quality of main materials, the mix design of asphalt mixture and the mixing of asphalt mixture.
6. The mixture ratio of asphalt mixture is unreasonable, and the oilstone is relatively large, so that the paved pavement will produce choking and flooding; The oilstone is smaller, and the road surface will be looser; Poor quality of mineral aggregate, poor aggregate crushing value and stone compressive strength, and high content of slender flat particles reduce the stability of pavement mixture and are prone to various pavement diseases.
7. The asphalt mixture is not evenly mixed. Sometimes, when the mixing equipment has an accident, the furnace has just started, or the material temperature is low and the water content is high, the material temperature will be uneven; When there is a problem in the screening system, the aggregate gradation changes greatly; Sometimes there is white material, which makes the pavement difficult to spread and shape; Too high temperature causes asphalt aging, which can not guarantee the paving quality of asphalt concrete; The mixing amount is too small, which leads to the situation of stopping work and waiting for materials, reducing the temperature at the joint, causing temperature difference and forming a ridge; When the transportation equipment is not matched or the driver's skill is poor, it will hit the paver, causing the fuselage to move backwards and form steps. The above factors are easy to cause poor flatness and surface compactness.
Third, the construction quality treatment
In engineering construction, although the construction quality control is well done, it is inevitable that some factors will cause quality problems, so corresponding treatment measures should be taken.
1. Basic requirements for dealing with construction quality problems
1. 1 Pay attention to comprehensive treatment, which means not only preventing the original accident from causing new accidents, but also paying attention to the comprehensive application of treatment methods. If the bearing capacity of the structure is insufficient, comprehensive applications such as structural reinforcement, unloading, increasing support and changing structural scheme can be adopted.
1.2 Pay attention to analyzing and eliminating the cause of the accident. This is not only a treatment direction, but also an important measure to prevent accidents from happening again. For example, the quality problems caused by subgrade flooding settlement should be eliminated, and drainage and dredging measures should be formulated to achieve solidification and stability as soon as possible. The treatment should be safe and reliable, leave no hidden dangers, meet the requirements of traffic opening, and make the construction party more economical and reasonable.
1.3 Correct selection of treatment time and method, timely analysis and treatment after problems are found, but not all quality problems are treated as soon as possible. Such as cracks, settlement and deformation instability, if it is not treated, it often fails to achieve the expected effect and needs repeated treatment. The selection of treatment methods should be based on the characteristics of quality problems, taking into account factors such as safety, reliability, technical feasibility, economic rationality and convenient construction.
1.4 correctly determine the treatment range. In addition to dealing with the accident site directly, we should also check the impact of the accident on the adjacent area and the whole structure to correctly determine the treatment scope. If the bearing capacity of slab is not enough for reinforcement, slab, beam, pier, column or wall may be reinforced to the foundation.
1.5 Ensure the safety during accident handling. There are many unsafe factors at the scene of the accident, so reliable safety technical measures and protective measures should be taken in advance and strictly checked and implemented.
1.6 Strengthen the inspection and acceptance of accident handling. From construction preparation to completion, inspection and acceptance shall be carried out according to the provisions of relevant codes and the quality standards required by the design.
1.7 carefully review the actual situation of the accident. In the process of accident treatment, if the accident situation is quite different from that described in the investigation report, the construction should be stopped. Find out the essence of the problem and take corresponding measures before continuing the construction.
2. Construction quality problems should be documented.
The following information should be needed to deal with general quality problems: first, the construction drawings related to accidents; Followed by accident-related information, such as: raw material inspection report, various test reports, construction records, etc. Third, the accident investigation and analysis report includes:
2. 1 accident situation: the time and place of the accident, the description of the accident, the observation records of the accident, the development and change law of the accident, whether the accident has been stable, etc.
2.2 Nature of the accident: whether it is a structural problem or a general defect, whether it is a superficial problem or a substantive problem, whether it needs to be handled in time and whether it needs to take protective measures.
2.3 Cause of the accident: The important cause of the accident should be made clear, such as whether the structural cracks are caused by uneven settlement of foundation or temperature deformation; Is it caused by construction vibration or insufficient bearing capacity of the structure itself?
2.4 accident assessment: explain the impact of the accident on the structural function, service requirements, structural mechanical properties and construction safety, and attach the measured, rechecked and test data.
2.5 Information about the personnel involved in the accident and the main responsible persons. Finally, the opinions and requirements of the design, construction and construction units on the accident.
3. Emergency measures to deal with construction quality problems
In the process of road and bridge construction, construction quality problems often occur. Quality problems in engineering are changeable, and often develop and change with the changes of time, environment and construction conditions. Some tiny cracks may gradually develop into component fractures, and some local settlement deformation may cause collapse. Therefore, before dealing with quality problems, we should analyze the nature of the problems in time and make judgments. For those deformations and cracks that change with time, temperature, humidity and load conditions, we should carefully observe and record them to find out the changing law and possible consequences. For those surface quality problems, it is necessary to further find out whether the nature of the problems will change, and for those vicious accidents that may develop into component fracture and collapse, emergency remedial measures should be taken in time. When formulating emergency measures, the following items should be paid attention to in general.
1) For dangerous quality accidents, the warning zone should be closed or set up first. It is not allowed to enter the site for treatment until it is confirmed that it cannot collapse or reliable support is carried out to avoid casualties.
2) For the parts that need to be partially demolished, the influence of the accident on the adjacent area structure should be fully considered to avoid further expansion of the accident, and reliable safety measures and demolition measures should be formulated to prevent the handling of the original accident from causing new accidents.
3) The structural strength, stiffness and stability in the treatment stage should be checked, reliable protective measures should be put forward, and the stability of the structure should be closely monitored during the treatment.
4) When strengthening the structure without unloading, attention should be paid to the influence of treatment methods and construction load on the bearing capacity of the structure.
5) We should fully consider the influence of the additional internal force generated during accident treatment on the structure and the unsafe factors caused by it.
Four. conclusion
In a word, the road and bridge engineering is long and wide, with strong seasonality, heavy workload, bitter construction conditions, lack of mature experience and advanced detection methods, which require us to make greater efforts to improve and gradually strengthen and improve quality management.
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