Tunnel construction With the rapid development of national infrastructure and the continuous expansion of its scale, in recent years, the construction of railways, light rail, maglev railway, expressways and urban high-grade highways across the country has reached a climax. Tunnel construction is an important link in railway, light rail and expressway construction. Therefore, the safety management of tunnel construction is the key to the safety of railway and highway construction. In recent years, the exposure rate of tunnel safety accidents is getting higher and higher, which makes the safety management of tunnel construction more and more concerned by the society. Tunnel construction has the universality and uniqueness of general engineering. Complex construction environment, harsh construction conditions and many uncertain factors have become several major characteristics of tunnel construction, which are important factors that cause construction safety accidents. This paper will put forward some suggestions to avoid common tunnel construction safety risks.
1, safety management environment in tunnel construction
Many research data show that the hidden dangers in tunnel construction have the following characteristics: first, the hidden dangers in tunnel construction are objective because of the complex geotechnical properties of the foundation and engineering hydrogeological conditions; Secondly, due to the limited survey and design data, imperfect design and calculation theory and the inevitability of some unexpected accidents in tunnel construction, tunnel construction risks are accidental and inevitable. Thirdly, in the process of tunnel construction, due to the imperfection of construction technology, construction technology and construction method, the construction personnel's incomplete compliance with rules and regulations will also have an impact on safety; Fourthly, due to the great disturbance of tunnel construction to the soil around the site, it is easy to affect the buildings around the site, residents' life and environment. Analysis of the causes of tunnel construction safety hazards can mainly be attributed to the influence of fire, flood and harmful gases. Tunnel leakage, fire and harmful gas can be prevented by effective ways and methods.
2. Causes and preventive measures of fire in tunnel construction.
Most of the tunnel fires occur in the process of tunnel use, but we can't ignore the fire prevention work in the construction process. There are many fire sources in tunnel construction. Because the interior of underground buildings is generally humid, it is easy to accelerate the aging of insulation layers and contacts of various electrical circuits and equipment, and it is easy to cause short circuits and excessive local resistance. Tunnel ventilation and wind speed are relatively high. Once a fire breaks out, it will spread quickly. Generally, artificial lighting is used in tunnels, but the illumination of artificial lighting is low. As long as there is a fire or power failure, it is dark underground, and it is very difficult for workers to escape. It is difficult to put out the tunnel fire, because it is difficult to find the fire source and ignition point in the early stage of the fire, and it is impossible to judge the size of the fire intuitively when the fire is found to have spread and expanded. All these reasons increase the loss of fire, and the prevention of tunnel fire is very important. Methods of tunnel fire prevention: 1. Setting of fire fighting equipment. Once a fire breaks out, the fire detection system can give an alarm in time, so that the construction personnel in the non-fire section of the tunnel can prepare for it. Fire-fighting equipment shall be set at fixed points in the tunnel to ensure that workers can put out small fires by themselves. Second, the setting of stage fire doors. In tunnel construction, fire doors can be set at intervals to reduce fire spread and loss. Fire doors are designed and installed according to national fire protection requirements. Third, the guarantee of emergency measures. Once a fire breaks out, there should be timely and effective treatment methods, and there should be considerable safeguard measures for personnel rescue, fire extinguishing scheme and economic property rescue to minimize the impact of the fire.
3. Causes and preventive measures of flood in tunnel construction.
In the process of tunnel construction, there are hidden underground reservoirs formed by underground water, which gush out after being blasted through or opened, or surface water and groundwater flow in through cracks, faults, subsidence areas and other channels. When the water inflow exceeds the normal drainage capacity, it will cause floods. The main reasons for water leakage in general tunnel construction are as follows: First, the reasons for survey and design. The survey of engineering geological conditions is inaccurate, because the survey is only a point survey, and then the underground geological conditions are predicted according to the point survey, so it is impossible to grasp the geological conditions very accurately. In addition, in terms of design, the calculation theory of tunnel waterproof and drainage design is not perfect, and the design standard is generally low. Many places that need to be strengthened, such as the laying scope of waterproof boards, the treatment of construction joints and deformation joints, and the setting of drainage ditches and blind ditches (pipes), have not been effectively strengthened. Investigation and design is one of the main causes of tunnel leakage. Second, material reasons. Improper use of building materials is also a hidden danger of engineering safety, especially waterproof materials. The thickness of waterproof materials used in tunnel construction can not meet the design requirements, and the strength is low and the quality is unstable. At present, the construction standard of tunnel waterproof materials in China is not perfect, which leads to some problems, such as unscientific laying quality detection method, poor smoothness of construction surface and lax protection of waterproof board during construction. In addition, in the actual construction process, the entry system of waterproof materials into the tunnel construction market was not established, and the way of winning the bid at a low price was adopted. The bid price of waterproof materials is out of line with the market price, and small enterprises often win the bid at ultra-low prices, resulting in unqualified raw materials flowing into the market. Third, the construction reasons. The neglect of safety in construction technology and methods has great influence on engineering safety. When the tunnel is excavated, the backfill is not well done or dense, and the support is not closely combined with the surrounding rock, forming a stagnant water space; Insufficient number of blind ditches (pipes) can easily lead to poor drainage or failure to effectively lead water to the drainage ditch; The concrete pouring is not strictly implemented, the mixture ratio control is lax, the tamping is not dense, and the impermeability grade can not meet the design requirements; The main reason of construction leakage is the insufficient strength of concrete formwork removal, which leads to cracks and leakage channels in concrete. Four, the reason of engineering quality inspection. Due to the backward detection methods at present, the quality problems existing in the construction are not easy to be found in time, such as loose concrete pouring and cavities inside, which is also a main reason for tunnel leakage. In view of the above reasons, how to reduce the impact of flood on tunnel engineering can be achieved mainly by improving design standards, strengthening construction quality management and enhancing the safety awareness of construction personnel. First, improve the measurement accuracy and design level. In order to improve the accuracy of geological survey, attention should be paid to selecting representative points with appropriate density. Design should be based on all survey data, in strict accordance with national and industry design standards. In the case of incomplete survey data, the entrusting party must be required to provide comprehensive survey data, and it is not allowed to guess out of thin air. Second, strictly control building materials, especially waterproof materials. There is a special acceptance mechanism for building materials entering the construction site, and unqualified building materials are not allowed to enter the construction site. Waterproof materials, in particular, should be strictly inspected before entering the site, specimens should be made in strict accordance with the construction technology and tested regularly. Third, strictly control the construction process. Carry out the construction in strict accordance with the specification requirements, strengthen the quality control of key processes: pay attention to blasting technology, reduce the disturbance and over-excavation of surrounding rock; Strengthen the quality control of concrete pouring, construct in strict accordance with technical requirements, improve the impermeability of concrete and the compactness of vault backfill, and reduce cracking; Strictly control the formwork removal time of lining concrete. Detailed construction technology control standards should be formulated for key processes, such as waterproof board construction technology standards, including waterproof board welding, laying and quality inspection. Strengthen training and supervision, strengthen the professional training of construction and supervision personnel, and strengthen supervision over the implementation of standards. Fourth, improve the quality of testing. Improve the inspection plan, find the quality problems in the project in time, and remedy them in time.
4, the causes of harmful gas in the process of tunnel construction and preventive measures
Harmful gases in tunnel engineering usually refer to natural gas, such as gas, methane CH4, carbon dioxide (CO2), hydrogen sulfide (H2S) and radon. These harmful gases are not only harmful to human health, but also combustible gases, which are often ejected suddenly, causing catastrophic damage. These harmful gases often appear in coal measures strata with relatively closed structure, and may also appear in non-coal measures strata. Most of the harmful gases are encountered in the tunnel construction across the coal seam, and a few are due to the construction near the coal seam, and the nearby geological structure is convenient for gas infiltration or transmission.
The prevention and control of harmful gases should also be based on the principle of prevention first and safety prevention. Long-term gas monitoring should be carried out during construction to effectively monitor gas concentration. Strengthen ventilation, dilute the harmful gases in the tunnel and discharge them out of the tunnel in time. Matters needing attention in the construction operation process are also very important. Taking measures such as not engaging in welding operations, using safe explosives during blasting and paying attention to the early discharge of harmful gases in tunnels can play a preventive role against harmful gases.
5. Conclusion
There is no shortcut to safety management, and the core lies in prevention. To do a good job in tunnel construction safety, we must adhere to safety first, prevention first and comprehensive treatment. In addition to the prevention of the above methods, it is also necessary to enhance the safety awareness of construction personnel and improve emergency measures. It is necessary to establish the idea of safety first, strengthen tunnel construction management and safety education for participants, improve their safety awareness, and strictly abide by the relevant provisions of safety production; Establish and improve various rules and regulations, improve the responsibility system for production safety, and conduct professional training on safety construction for on-site operators. Only after passing the examination can you take up your post, otherwise you may not enter the site. In the process of construction, we should accurately grasp the omen and emergency measures of water leakage, water seepage and other emergencies, strictly implement the monitoring system of the project, implement the corresponding monitoring frequency, record in time and feedback information to the relevant competent departments. If there is any abnormality, the operation shall be stopped immediately, remedial measures shall be taken actively, and the operators shall be evacuated, and the construction shall be continued after the danger is eliminated, so as to ensure the personal safety of the operators. The safety management of tunnel construction is an urgent and long-term work. By perfecting the safety responsibility system, strengthening the construction of safety system, perfecting the safety emergency plan, strengthening the on-site safety management, improving the safety quality of personnel and strictly controlling the construction process, it will play an effective role in the safety management of tunnel construction.
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