In recent years, with the continuous development of highways, tunnel fire accidents have occurred frequently around the world, which has attracted widespread attention. From the Channel Tunnel fire in 1996, the Kitzsteinhof Mountain Tunnel Fire in Salzburg, Austria in 2000, the subway tunnel fire in South Korea in 2003, to the Zhenwushan Tunnel Fire on the Chongqing-Guizhou Expressway in China in 2004, and the 2008 Accidents such as the fire in the southbound Dabaoshan Tunnel of the Shaoguan section of Guangdong's Beijing-Zhuhai Expressway in 2016 have caused huge casualties and property losses. It can be said that tunnel fire accident rescue, like high-rise building fires, has become a major problem faced by countries around the world. At the same time, it is also an important topic for firefighting forces to explore and study fire-fighting and rescue techniques and tactics.
The Shanghai-Chongqing Expressway, numbered G50, is one of the main trunk lines of the east-west horizontal line of the national expressway network. It is an important transportation artery connecting the western region of my country to the eastern region. It is 1,900 kilometers long and passes through Shanghai and Jiangsu. The five provinces and cities of Anhui, Hubei and Chongqing will be fully connected by the end of this year. It is currently one of the most difficult highway projects in the country. Tunnel construction is rare in the country. The Shanghai-Chongqing Expressway passes through Shizhu Tujia Autonomous County, from Lengshui at the junction of Shizhu and Lichuan in Hubei to Mozi at the junction of Shizhu and Zhongxian County in Chongqing. The total length of Shizhu is 66 kilometers. There are 4 tunnels and one short tunnel (Yueeryan). Tunnel 195 meters), one long tunnel (Zhulinping Tunnel 1,450 meters), two extra-long tunnels (Fangdoushan Tunnel 7,600 meters and Lujialiang Tunnel 6,645 meters), (Note: According to the national highway industry tunnel classification standards, extra-long tunnels ≥ 3,000 meters, 3000 meters lt; long tunnel ≤ 1000 meters, 1000 meters lt; medium tunnel ≤ 500 meters, short tunnel lt; 500 meters). Among them, the Fangdoushan Tunnel is reported to be the longest expressway tunnel in Chongqing and ranks among the top in the country. As the first large-scale highway tunnel project in Shizhu County, it is both the focus and difficulty of fire safety protection. Especially after the Shanghai-Chongqing Expressway is completed at the end of this year, the traffic volume in the tunnel will increase exponentially, which will greatly increase the risk of fire accidents. Through on-the-spot investigation of the current construction situation of the Fangdoushan Tunnel Project, the author made the following thoughts on how the firefighting force can quickly and effectively carry out rescue operations in the event of a fire accident.
1. Overview of Fangdoushan Extra Long Tunnel
(1) Design form. The Fangdoushan Extra Long Tunnel is located at km 1,649 of the Shanghai-Chongqing Expressway. It adopts the design standard of a four-lane fully enclosed expressway. It is a separate tunnel with one-way travel up and down. It has a total length of 7,600 meters and a design speed of 80 kilometers/hour. The one-way tunnel net Width 10.5 meters, clear height 5 meters.
(2) Fire-fighting facilities. A ring-shaped fire water supply pipe network is set up in the tunnel. There are two water inlet pipes with a diameter of 100 mm between the upper and lower lines. The water pressure is maintained by a high-level pool. The pipe network pressure is 0.3Mpa. When the water pressure is insufficient, it is supplemented by a fire pump. A fire hydrant box is installed every 50 meters in the longitudinal direction of the tunnel, which contains hoses, water guns, AFFF pipe guns and AFFF liquid. It is also equipped with two 4kg ABC dry powder fire extinguishers and two water-forming foam fire extinguishers. Film foam fire extinguisher. Two above-ground fire hydrants are set up near the two entrances outside the cave for fire extinguishing needs.
(3) Fire alarm facilities. An advanced automatic fire alarm system is used in the tunnel, which has the characteristics of high sensitivity and extremely low false alarm rate. There are temperature-sensitive optical fiber detectors and monitoring probes in the center of the top of the tunnel, and a temperature-sensitive optical fiber host is installed in the monitoring room; every other There is a manual alarm button 50 meters away and wired telephones every 200 meters. Once a fire occurs, people trapped in the tunnel can transmit fire information to the fire alarm host in the control room through manual alarm buttons.
(4) Smoke prevention and exhaust facilities. Three groups of 20 large jet fans are installed in the upstream and downstream tunnels of the tunnel for smoke exhaust and air supply. The operation of the fans is linked to the fire monitoring system. In addition, vertical smoke exhaust shafts are also installed in the tunnel, and horizontal holes for pedestrians (vehicles) can also be used for natural smoke exhaust, which basically meets the needs of fire extinguishing and smoke exhaust.
(5) Safe evacuation facilities.
In view of the characteristics of extra-long tunnels, in order to facilitate evacuation, in addition to emergency alarm telephones, emergency broadcasts are also set up in the tunnel. Emergency parking zones are set up every 1,000 meters, pedestrian (vehicle) crossings are set up every 800 meters, lighting systems and light driving signs are set up in the tunnel, and light evacuation signs are set up at the entrance of the horizontal opening to facilitate the quick escape of trapped people.
(6) Other facilities. In order to meet safety requirements, 12mm thick SD type high temperature resistant heat insulating and fireproof coating is used inside the tunnel, with a fire resistance limit of 2-3 hours. At the same time, return yards are set up at both ends of the tunnel. In addition, all fire-fighting electrical equipment in the tunnel meets the first-level load power supply requirements and has independent power supply. At the same time, the Shizhong Expressway Management Center has set up a monitoring center to monitor the tunnel 24 hours a day. Once an accident occurs in the tunnel, the monitoring center can mobilize emergency rescue forces to the scene as soon as possible.
2. Main characteristics of fire accidents in extra-long expressway tunnels
(1) The combustion spreads quickly. Since vehicle fires are the main danger of tunnel fires, most vehicle fires are caused by short circuits in electrical circuits, carburetors, pneumatic systems of trucks, and collisions between vehicles. Every car has a fuel tank, and some of the cargo they carry are flammable materials. Once a fire breaks out, the temperature of the fire source is high and the combustion spreads quickly. If the vehicle carries flammable and explosive materials and there are many vehicles involved in the accident, this will intensify the combustion and the rapid development of the fire.
(2) Smoke spreads quickly and is highly toxic. Since the extra-long tunnel is a long and narrow tubular space, when a fire occurs, the fire area will be filled with thick smoke. Under the action of high-temperature hot air pressure, most of the smoke formed accumulates in a limited space due to the limited holes for smoke diffusion. Therefore, in a unit three-dimensional space, the amount of smoke is greater than the number of units in other building fires, and the smoke produced by combustion is highly toxic, which will significantly reduce the oxygen content in the space, and it is easy to cause death to personnel under hypoxic conditions. Suffocation, even death.
(3) Rescue and evacuation are difficult. Due to the few entrances and exits and the long and narrow internal passages in the extra-long tunnel, it is almost in a closed space. Once a fire breaks out, due to the influence of factors such as thick smoke, high temperature, and accumulation of toxic smoke, rescuers will not be able to directly observe the location of the fire, the scope of the fire area, and other factors after arriving at the scene. When the trapped personnel are located, evacuating people, vehicles and materials is almost equivalent to pulling out a tooth from a tiger's mouth.
(4) It is difficult to dispose quickly. Expressway tunnels are generally far away from urban fire brigades. In the early stage, fires are easy to get out of control, and there is little room for maneuver on site. Once a traffic fire accident occurs, it is easy to cause traffic jams, which will directly prevent firefighting vehicles from quickly arriving at the scene. After the fire trucks arrived, they had to evacuate the vehicles and people who had entered the tunnel. It was difficult to provide water to the fire. Once the fighter jets were lost and the fire was out of control, the tunnel would quickly become a hellish maze, allowing combatants to penetrate deep inside. Fire reconnaissance, personnel evacuation, close combat fire fighting and rapid disposal will become very difficult.
(5) The requirements for accident handling are high. Due to the structural characteristics of the highway tunnel, after a fire occurs, it not only burns violently, but also has a high risk of explosion, high temperature, rapid spread, thick smoke and low visibility, making the rescue and fire-fighting tasks "urgent, difficult and dangerous". There is a lack of attack roads, little room for maneuver, and difficulty in approaching the fire point. The attack direction will be restricted by the outside wind direction, and it is difficult to grasp the location and burning range of the fire. If hazardous chemicals or highly toxic items leak and explode, it is difficult to imagine what consequences will be caused. Therefore, difficult and dangerous firefighting spaces, harsh and narrow firefighting environments, and difficult-to-control dangers will put forward higher requirements for firefighting tactics, self-protection, and firefighting equipment.
(6) The disposal time is long and the organization and command are difficult. Fighting fire accidents in extra-long highway tunnels involves high hazards, losses, difficulty, long time, and long fronts. It is also very difficult to organize backup personnel, equipment, and effective supply of supplies. At the same time, more suggestions have been put forward for the establishment of on-site command headquarters, the quality of commanders, the effective command of combat operations on both sides of the tunnel entrance and the coordinated handling of relevant functional departments, especially the problem of communication shielding and on-site communication liaison support. High requirements.
3. Some thoughts on how to quickly and effectively carry out fire-fighting and rescue operations in extra-long tunnels
(1) Focus on solving the problems of air supply and smoke exhaust in tunnels
1 , The importance of air supply and smoke exhaust
The ventilation and smoke exhaust facilities set up in the tunnel are determined by the building structure of the tunnel. Compared with ground buildings, tunnel engineering structures have complex structures, closed environments, narrow passages, few evacuation exits to the ground, and long escape paths. When a fire occurs, not only does the fire spread quickly, but the accumulated high-temperature and dense smoke is difficult to remove naturally and spreads rapidly in the tunnel, making it difficult for personnel evacuation, fire-fighting and rescue operations, and seriously threatening the lives of trapped people and rescue personnel. Due to the constraints and limitations of the tunnel structure and the influence of vehicle exhaust gas passing through the tunnel, the oxygen content in the air inside the tunnel is relatively low compared to that outside the tunnel. After a fire occurs in the tunnel, a large amount of incomplete combustion products will be produced ( Such as: CO), forming dense smoke that spreads rapidly. According to tests, the spread speed of smoke in a fire is five times faster than that of fire. Fires in tunnels should be regarded as a fire source. Due to the influence of the tunnel space, the spread speed of smoke is quite alarming. Generally, when a fire occurs It begins to spread after about 5 minutes, and the concentration reaches its maximum at 15 minutes. The diffusion of smoke reduces visibility, and the CO mixed in the spreading smoke is a colorless, odorless, highly toxic flammable gas, which is extremely harmful. When the CO content reaches 0.5/above, death will occur within 2-3 minutes.
2. Use fixed ventilation and smoke exhaust facilities
The ventilation and smoke exhaust system of the Fangdoushan Extra Long Tunnel is a unified and independent system, consisting of jet fans, silencers, air ducts, and air outlets. (The smoke exhaust system includes a wind pavilion), which exhausts smoke through the tunnel entrance and the shaft in the tunnel. After the system is turned on, the jet fans in the tunnel supply air in the same direction, and the flue gas flows in a horizontal direction. In the event of a fire, it will inevitably have a certain impact on rescue tactics and measures. The principle of smoke exhaust in the tunnel is to supply air in the opposite direction to the safe evacuation direction of passengers. This can not only prevent the smoke from flowing in the same direction as people, but also provide fresh air to the evacuated personnel. The Fangdoushan Tunnel adopts a double-hole design, so in the event of a fire, the vehicle in front of the accident vehicle can be evacuated directly; the vehicle behind it will stop immediately after being blocked, and the passengers will abandon the vehicle and escape in the opposite direction. This determines the ventilation and smoke exhaust method in the tunnel: supply air to the driving direction and exhaust smoke at the other end.
3. Use mobile ventilation and smoke exhaust equipment
When a power outage occurs or fixed facilities are damaged in a fire, and the ventilation and smoke exhaust needs in the tunnel cannot be met, mobile ventilation must be used. Smoke extraction equipment. Through calculation, when the tunnel is under normal conditions (calculated driving speed is 50km/h), the allowable concentration of CO is 200ppm and the allowable concentration of smoke is 7.5×10-3m-1; when there is a traffic jam (the minimum driving speed is 10km/h), the average CO concentration The allowable concentration is 300ppm, and the allowable concentration of smoke is 9.0×10-3m-1; in addition, the wind speed in the tunnel should meet the wind speed required to dilute the odor in the air. The fire scale in the tunnel is designed according to 20MW. When longitudinal smoke exhaust is used, the wind speed in the tunnel is required to be 3m/s. Currently, most of the mobile smoke exhaust equipment equipped by firefighting forces are electric smoke exhausters, water-driven smoke exhausters, etc., which are a "sharp sword" for dealing with tunnel fire accidents.
(2) Quickly and effectively implement rescue operations in tunnels
Studies on tunnel fire cases at home and abroad have found that many tunnel fire rescue errors are mainly concentrated in several aspects. First, the smoke exhaust and air supply were unfavorable during the rescue process, and the thick smoke made it difficult to evacuate personnel; second, the respiratory protection time limit was limited and could not meet the rescue needs; third, the air supply was unfavorable, affecting the continuity of the rescue work and delaying on-site rescue operations. . Once a fire accident occurs in a highway tunnel, in order to carry out rescue operations quickly and effectively, it is necessary to make corresponding preparations in accordance with relevant requirements.
1. Be prepared for battle
(1) Centrally move smoke exhaust and air supply equipment at the fire scene
In order to ensure the normal operation of the air supply and exhaust system in the tunnel Under the premise of ensuring the safety of the disaster, mobilize as many mobile air supply and smoke exhaust equipment as possible to the disaster response site to increase the air supply and smoke exhaust capacity.
High-power smoke exhausters are used to implement positive pressure air supply and negative pressure smoke exhaust at the entrances and exits at both ends of the tunnel. The flow direction of smoke is artificially controlled to ensure that there is no smoke damage in the escape passage and to ensure the safety of rescuers and rescued personnel.
(2) Strengthen personal protection
In order to ensure the safety of rescuers during fire fighting and rescue, personnel entering the tunnel must strengthen personal protection and wear respirators. Depending on the combat area, ordinary fire fighting suits, heat insulation suits, fire avoidance suits, etc. are required as required. Since the handling of disaster accidents in tunnels takes a long time and requires a lot of physical effort, the respirator should be a 4-hour self-circulating oxygen respirator or a 2-hour double-cylinder air respirator that can provide long-term breathing protection.
(3) Ensure gas supply
After a fire accident occurs in the Fangdoushan Expressway Tunnel, mobile gas supply trucks from Zhongxian County, Dianjiang and the Special Service Detachment should be mobilized in a timely manner. Mobile gas supply stations were set up at the two entrances and exits, and a gas cylinder transport team was organized to transport gas cylinders to the front. On-site gas bottles should be placed in a centralized place in a cool place to avoid exposure to high temperatures to ensure a cool and comfortable air source.
(4) Establish a tunnel war zone
The firefighting forces within a 5-minute drive from the tunnel entrance and exit will form a tunnel war zone as the first dispatch force to deal with the Fangdoushan Tunnel fire accident. In order to ensure that the combat operations of all participating forces are carried out quickly, organized and coordinated, special training must be organized and carried out. Each participating force is divided according to its tasks: fire reconnaissance team, fire smoke exhaust team, communication and lighting team, personnel rescue team, engineering team Demolition team, fire fighting team, etc., each team carried professional equipment to carry out rescue operations.
2. Standardize combat operations
(1) Strengthen mobile gas supply security
The total length of the Fangdoushan Tunnel is 7.6 kilometers. In the event of a fire, personnel must be removed from the For a successful rescue in a tunnel, the air supply capability of the rescue force is crucial. After field testing, when rescuers wearing ordinary air respirators reach the most unfavorable point of the tunnel (i.e., the middle of the tunnel), the remaining air volume is difficult to meet the needs of firefighters for rescue operations. Therefore, personnel operating deep inside must wear long-lasting breathing apparatus - double-cylinder air breathing apparatus or self-circulating oxygen breathing apparatus, which can allow firefighters to reach the middle of the tunnel and work for at least 30 minutes. At the same time, teams are used as units to carry mobile air supply sources as backup air sources for trapped persons or rescuers to use in emergencies. It is not recommended that rescuers take off their own respirators and give them to trapped persons. Rescuers work in teams, with each team consisting of five people carrying a mobile air supply source.
(2) Ensure smooth escape passages
The pedestrian (vehicle) crossing in the tunnel is not only a life passage for trapped people to escape, but also an attack passage for firefighters to attack from inside. . During the rescue period, the escape passage must be well ventilated, well-lit, and always under positive pressure to prevent smoke from intruding. Since the passage is narrow and long, an air blower should be placed at the pedestrian (vehicle) crossing selected for internal attack and rescue to supply air to the passage.
(3) Stabilize the emotions of the trapped people
After a fire occurs in the tunnel, the tunnel broadcasting system must be used immediately to inform the trapped people of the correct escape methods and the use of fixed fire-fighting facilities. method, and use the recording system to play it repeatedly. Firefighters who go deep into the tunnel to carry out rescue operations must use portable loudspeakers to shout to stabilize the emotions of the trapped people and cooperate with the rescue operations.
(4) Guide evacuees to vehicles
Rescuers carry work lights and strong lighting lamps into the tunnel disaster site, lay luminous life-saving lighting lines along the evacuation channels, and place self-storage lamps and adsorbed luminous guide signs, etc., and use lighting trucks to introduce mobile lighting. At the same time, dedicated personnel will be assigned to stay at key locations where people may get lost to guide the evacuated people to evacuate along the correct route. At the same time, we cooperated with the highway rescue team and traffic police to evacuate blocked vehicles in the tunnel in an orderly manner.
(5) Rescue people trapped in tunnels
People who are able to move can be guided by rescuers to evacuate along the escape passage; for those trapped with minor injuries due to crowding or collision, Personnel can be helped to escape passages by rescuers, and then transferred to the medical emergency department after simple treatment; critically injured people who are in a coma or are seriously injured and unable to move must be transported on a body-fixed stretcher. During the process of rescuing people, rescuers should provide necessary protective equipment for the rescued person, such as the accessory mask of a double-mask air respirator, a double-mask with a mobile air supply source, or a simple anti-smoke mask that can be carried with them.
(6) Comprehensive search, demolition and rescue
In order to ensure that all trapped persons can receive timely rescue, search and rescue should be adhered to throughout the entire process of fire extinguishing and rescue, and every person should be searched thoroughly corner. Especially for accident vehicles and vehicles that are blocked in tunnels and cannot be evacuated in time, special equipment such as infrared vision cameras, hydraulic demolition equipment groups, and two-wheeled opposite-direction cutting machines must be used to demolish the vehicle body and carry out comprehensive search and rescue.
(3) Vigorously solve the communication problems in fire accident rescue in extra-long tunnels
To solve the communication problems in fire accident rescue in extra-long tunnels, make full use of the internal communication facilities of the tunnel. Quickly set up a fire scene communication network to ensure smooth wired and wireless communications.
1. Tunnel internal communication facilities
Tunnel internal communication facilities are divided into dedicated communication facilities and public communication facilities. Among them, special communication facilities are divided into: tunnel dispatch communication system, traffic signal control system, automatic fire alarm system, video surveillance system and broadcast amplification system; public communication facilities include: public wired telephone communication system and radio communication system. The existing tunnel dispatching private network (wired) and public mobile communication network (wireless) can be used as a communication command method for initial fire rescue. However, we cannot rely solely on the above systems. In the event of a fire, the firefighting force must also be equipped with underground mobile phones. Communication equipment can continue to establish an on-site communication and command network even if the above facilities fail.
2. Tunnel fire disaster site communication networking steps
(1) Establish the communication command of the front-line squadron. After the squadron in charge arrives at the scene, it should first use fixed communication facilities in the tunnel (such as tunnel dispatching communication dedicated network, mobile phones, tunnel amplified broadcasting, etc.) to establish underground and above-ground communication links. When fixed communication facilities are unavailable, use wireless Communications extension equipment establishes effective communications and conducts rescue and disposal operations.
(2) Establish an on-site communication command center
Use vehicle-mounted equipment to establish an on-site communication command center and open on-site command wireless communication network, wired communication network, computer communication network, satellite image transmission and Broadcast, complete the establishment and maintenance of wired and wireless communication links between the fire rescue headquarters and other rescue departments such as local government, public security, first aid, and highway management centers, transmit on-site images to the 119 command center through satellite transmission equipment, and accept and convey superior commands. Department and 119 command center orders.
4. Some Suggestions
The completion and opening of the Shanghai-Chongqing Expressway marks the completion of the entire east-west corridor in my country. At the same time, the Fengshi Expressway project is currently under construction. It will also be completed and opened to traffic in 2012. In view of the outstanding characteristics of highway tunnels, in the next few years, the southeast Chongqing fire brigade must have the ability to handle fire accidents in extra-long tunnels. What preparations should we make to face challenges?
1. Establish an emergency command system for fire accidents in extra-long tunnels to achieve rapid response, unified command, division of labor and coordinated operations.
2. Improve the fixed fire-fighting facilities inside the tunnel, and improve the actual fire resistance and efficiency of evacuation signs, sprinklers, smoke exhaust, fire hydrants and other facilities in the tunnel.
3. The fire command center and the tunnel management center establish wired and wireless hotline connections, and connect the tunnel monitoring images to the fire command center so that the fire department can grasp the disaster scene situation in a timely manner.
4. Develop and equip underground extension equipment for wireless communications to give full play to the advantages of wireless communications in fire fighting and rescue.
5. Strengthen the equipment construction of the fire brigade, and add special emergency rescue equipment to squadrons with extra-long tunnels within their jurisdiction.
6. Establish a full-time tunnel emergency rescue team and carry out relevant professional rescue training.
Hope to adopt it! ! ! !