Tunnel safety problems and countermeasures
At present, tunnel bolting and shotcreting technology has been widely used in municipal tunnel construction in China. The construction technology is stable, firm, safe, fast and convenient. Once introduced, it was quickly popularized and widely used in some thermal and electrical underground projects. It has been several decades since the introduction of bolting and shotcreting technology, so all the construction procedures are basically formed and the construction technology is relatively mature. At present, some small tunnels in municipal engineering usually have two linings, the initial payment is sprayed concrete, and the second lining is cast-in-place concrete.
Safety problems and countermeasures in initial support construction
There are many hidden dangers in the initial support construction of municipal engineering tunnels, among which water leakage, poisoning, collapse, electric shock and falling are the most common. These problems and their preventive measures are analyzed and discussed one by one. (1) water leakage, water leakage accidents often occur in tunnel construction, which will not only affect the structural safety of the tunnel, but also cause water leakage problems, causing great security risks. Therefore, it is necessary to monitor the soil moisture during excavation, and once it is found that the soil moisture becomes larger, the length of each excavation step should be shortened as much as possible. For some small areas of water leakage, the conduit can be buried to concentrate the water flow and flow out of the tunnel along the drainage pipeline, while for some large areas of water leakage, the construction needs to be stopped immediately to completely eliminate the nearby water source. When monitoring soil moisture, if it is found that the soil moisture is very high, you can set up a plate shed or a pipe shed, and choose the appropriate steel pipe density, thickness and length according to the construction site conditions and soil moisture. (2) Poisoning. Because the environment of tunnel construction is usually relatively closed, it is particularly important to ensure air quality. Before construction, you should be familiar with the direction of underground pipelines, especially some gas pipelines. These pipelines are generally buried within 5 meters, so be careful not to be damaged during construction, causing gas leakage. Secondly, tunnel excavation will inevitably encounter some humus. If the air is not circulated for a long time, it will lead to poisoning or suffocation of construction personnel. Therefore, in order to improve the air quality in the tunnel, it is necessary to do a good job of ventilation in the tunnel with the help of high-power exhaust fans. (3) Collapse, tunnel construction collapse is usually caused by the long excavation steps in front, and the sand layer and excavated soil encountered during excavation are backfilled. Therefore, we must be familiar with geological conditions and topographic conditions before construction. When encountering sand layer, the method of grouting and sand fixation with advanced small pipe can be used for treatment. At present, there is no better treatment scheme for backfill soil. Short excavation and quick spraying are usually used to reduce the arch distance, and some supporting measures are needed when the amount of backfill soil is large. In addition, because chemical materials usually only last for a certain period of time, it is necessary to control the time during excavation. For some small-scale collapses, in order to prevent them from causing large-scale collapses, an old woven bag can be laid outside as a simple support for supporting the arch. (4) Leakage. The connecting materials in tunnel construction are mostly steel. Once a leakage accident occurs, it will bring great threat to the personal safety of the construction personnel. Therefore, it is particularly necessary to do a good job in leakage prevention in municipal tunnel construction. The lighting power supply in the tunnel must use low voltage, and ensure the primary leakage of the power supply. In addition, in order to prevent the lines from getting wet or bumping, all lines must be wired on the wall. Tunnel lighting only needs to meet the brightness required for normal construction, and transformers should be used as much as possible to prevent construction workers from abusing electricity at night.
Safety problems and countermeasures in secondary lining construction
In the construction of secondary lining, the side wall and vault are usually supported as a whole first, and then poured together. The following problems should be paid attention to in the construction of the second lining of municipal tunnels: First, concrete is usually pumped by ground pumps, so it is necessary to use shock-free concrete, and the dosage of retarder should be controlled well. When pumping concrete, the principle of from far to near is usually followed. Secondly, when pumping concrete, it is necessary to control the speed, and it is necessary to set up special construction personnel to check the concrete formwork with the pouring progress, so as to control the pouring speed and reduce the slump of concrete, especially when the tunnel goes up and down. Too fast pouring speed or inappropriate concrete will lead to formwork deformation, which will lead to serious construction accidents. Finally, in the process of tunnel construction, we should always check the full house support and the concrete pouring position in the tunnel. Once the top wire is found to be cracked, the construction should be stopped immediately and reinforced. After a pouring gate is poured, the pouring speed should be slowed down appropriately, and then pouring should be started one by one after the inspectors have checked and given the operation instructions.
Bridge construction safety problems and solutions
There are many processes in bridge construction that cannot be repeated, especially the pile foundation structure of the bridge. Its construction quality is related to the stability of the whole bridge, and it is almost impossible to repeat the construction after the completion of pile foundation structure construction. When there is a problem, we can only take remedial measures such as piling. Therefore, special attention should be paid to the construction quality of pile foundation in bridge construction. In addition, the quality problems of pile foundation construction will bring many security risks. There have been pier collapse accidents caused by the quality of pile foundation construction, causing many casualties. Therefore, the construction of bridge and culvert pile foundation must standardize the construction operation, improve the safety management on the construction site, check the stability of key parts such as formwork and bracket when pouring pier columns, ensure the stability of pier columns, control the pouring speed during concrete pouring, and always pay attention to formwork to minimize accidents. At present, municipal bridge construction usually adopts underwater cast-in-place pile, and its construction follows the steps of drilling, hole-forming, cage-lowering, pipe-lowering and pouring. Attention should be paid to the following problems in construction: First, check the air tightness of the catheter before use, and check whether the aprons and threads are complete during installation. If there is a small amount of water leakage during pouring, it usually occurs on the lower conduit. At this time, it is necessary to speed up the concrete pouring and plug the leaking parts by deepening the buried depth of the conduit; Secondly, the broken part of the spiral steel bar on the reinforcing cage can't face inward, otherwise the conduit will probably be hoisted when pouring. Because it is pouring, if the conduit is stuck, it will bring a lot of unnecessary trouble, so the broken part of the spiral steel bar should be tied outside the cage to prevent the conduit from being stuck without being pulled up. The third is to control the slump of concrete. Excessive concrete slump will cause concrete segregation, while too small concrete slump will easily lead to pipe plugging. Fourth, we should grasp the opportunity when lowering the reinforcing cage. If the speed is too slow, it is easy to cause the sediment at the bottom of the pile to thicken or cause hole collapse, which will bring unnecessary trouble to the later concrete back sealing pouring.
The municipal tunnel bridge and culvert project is related to the construction of people's livelihood and plays an important role in promoting the development of national economy. In order to improve people's living conditions and promote China's economic development, China's investment in municipal public facilities is increasing every year. However, the municipal tunnel bridge and culvert project has a strong system complexity, and its final quality largely depends on the quality and safety control in the construction stage. Therefore, in the construction stage of municipal tunnel bridge and culvert engineering, effective safety control system must be adopted, and reasonable safety management measures should be taken to fully reduce the project quality risk and provide people with more reliable and safe infrastructure.
For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd