As the development of road traffic brings rapid economic development, the construction of roads and tunnels is becoming more and more common. Under normal circumstances, during the tunnel lining construction, concrete often has problems and defects such as leaking bars, pitting and cracks. Although it has no direct impact on the actual use of the structure and the internal quality, due to its relatively high probability of occurrence, the lining The aesthetic appearance is affected to a certain extent, and the overall quality of the lining is reduced.
The factors affecting the tunnel lining concrete
(1) Freeze-thaw damage of concrete
Concrete has certain pores and expands after freezing. When the water retention of the concrete is high and the volume in the pores is small, the problem of excessive pressure will occur, and during the freezing and thawing process, the moisture on the surface of the concrete will be affected by the osmotic pressure, resulting in damage to the concrete.
(2) Constituent materials of concrete
In the process of on-site concrete mixing, the use of different materials directly affects the durability of the concrete. In some specific processes, the diameter of the cement particles will become thinner and thinner. Under such conditions, high heat of hydration will be generated. At the same time, the problems of high temperature difference and high shrinkage rate, concrete collapse is increasing, and the particle size of the aggregate is reduced to increase its workability. The addition of cement and admixtures also exacerbates the problem of heat of hydration, which directly leads to more serious problems of shrinkage and deformation of concrete.
(3) Rebar corrosion
If the concrete is in a highly alkaline environment for a long time, the surface of the steel will be oxidized to form a passivation film, which will not be damaged by rust. If the protective layer of concrete reinforcement is carbonized, it will cause a decrease in alkalinity, resulting in some air and moisture inside the concrete, which will lead to corrosion of the reinforcement.
Defect analysis of tunnel lining concrete
The defects of tunnel lining concrete construction mainly include leaking bars, pitted surfaces, holes, etc., and the solutions to these defects. For details, please see “TREATMENT AND PREVENTION OF TUNNEL LINING CONCRETE DEFECTS”
Treatment measures for defects in tunnel lining concrete
(1) Conduct a detailed site survey
In order to make the tunnel construction proceed more smoothly, and to further ensure that the repaired concrete pavement is stronger, it is necessary to carry out certain surveys on the local construction road sections and determine the construction plans in different areas before the repair, which is difficult for the construction Obtained, the region chooses the construction plan that is most suitable for it. This is the preparation work before construction. This can to a certain extent promote the concrete to be completed within a fixed period of time, and can further consolidate the quality of the road section. During the process of topographic survey In the process, it is necessary to investigate the soil moisture content and settlement of the soil, which will further make the later construction more perfect. When the survey is completed, all factors need to be more comprehensively improved, based on the relevant influencing factors. More suitable for construction.
(2) Choose the right concrete material
When the material is artificial, it is necessary to carry out certain experiments to verify the performance of the material before using it, and in order to make the material can be connected with the concrete and other interface materials: it has better adhesion, so it needs to ensure that its edges and corners are clear. The mud content of related materials has clear requirements, that is, the mud content cannot exceed 1%. When the mud content in the material is high, the concrete structure composed of it will not be able to withstand high bending resistance. And when the wall surface is dry, due to the difference in temperature, it is easy to cause large deformation. Therefore, the actual relevant content needs to be more clearly defined. In the selection of raw materials, especially for the first stone, etc. More clear management of materials, etc.
(3) Choose the right gravel gradation
In the selection of crushed stone, the following judgments need to be made: the gradation of crushed stone needs to be guaranteed. When the particle size of the stones is large, since the gaps between the stones cannot be completely filled with concrete, it is likely to cause many gaps between them, which will greatly reduce the bearing capacity of the concrete, and when the particle size is small Because it requires a large amount of bonding material to bond it, when the particle size of the stone is small, the amount of cement will be greatly increased, which will increase the cost of the project.
(4) Ensure the quality of lining concrete pouring
At present, concrete transportation is mainly carried out by concrete trucks. During the transportation process, it is necessary to pay attention to the control of the water in the concrete, so that the water content of the concrete is within a certain range. When the concrete truck needs to be transported as much as possible Reduce the number of times of parking, and reduce the time spent on the road as much as possible, so that concrete can enter the link of people’s pouring faster, so that the quality of concrete is guaranteed to a certain extent.
In summary, in the actual construction process of tunnel lining concrete, it needs to be based on prevention. If problems occur, they should be resolved at the first time, and the experience and lessons of specific defects should be continuously summarized. At the same time, it is necessary to strengthen the emphasis on process control, combine the requirements and standards of coagulation and construction, scientifically implement the relevant work quality, and use scientific methods to promote the overall improvement of the construction quality of tunnel lining concrete.