China's Subway Fire Safety Problems and Countermeasures

Abstract : It is of great realistic significance to study how to prevent subway fire accidents because fires in subways will cause huge casualties and property losses. Based on the status quo of China's subway development in recent years, the main fire problems that existed were summarized, and the countermeasures and suggestions for strengthening the safety of subway fires were put forward.

Keywords : fire safety ; subway ; fire risk ; evacuation

In recent years, with the rapid development of China's social economy, the process of urbanization has been accelerating, and the total amount of urban traffic demand has also been increasing rapidly. The contradiction between urban transportation and transportation has become increasingly prominent. Compared with the traditional ground transportation mode, the subway, as an important tool for urban transportation, has the advantages of large capacity, high speed, punctuality, convenience, energy saving and environmental protection, and plays an increasingly important role in improving the urban traffic environment. Many cities are widely used. At the beginning of the 21st century, there were only 7 subway lines in 4 cities in China , with a total length of 146 kilometers . By the end of 2014 , there were 22 cities in the country with 95 subway lines, and the total length of subways reached 2 900 kilometers . There are many cities under construction, approved construction, and planning and construction of subways. It is expected that by 2020 , the total mileage of China’s subways will reach 6,100 kilometers .

With the rapid development of urban subways, the fire safety issues of subways are getting more and more attention. Subways have the characteristics of large passenger flow, dense population, closed space, and complex facilities and facilities. Once a fire occurs, evacuation of people and fire suppression are extremely difficult, and it is easy to cause major casualties, serious economic losses, and bad social impact. Therefore, we must pay attention to the analysis of the problems existing in subway firefighting and formulate corresponding measures.

First, the problem of subway fire

( I ) Incomplete specifications

Subway is a very complicated transportation system and it needs perfect design specifications as a guide to fire safety. At present, national standards, "Metro design specifications" (GB 50157 - 2013), " Urban Rail Transit technical specifications" (GB 5049 - 2009), " architectural design code for fire protection" (GB 50016 - 2014) and so on. Many of the opening of the metro cities have also developed a corresponding local standards, such as "urban rail transit engineering design specifications" in Beijing (DB 11/995 - 2013) , Shanghai, "Urban Rail Transit Design and specifications" (DGJ 08 - 109 - 2004) . These specifications provide design requirements for power supply, signal, water supply and drainage, and disaster prevention in subway projects, but they are not considered comprehensively in the design of fire safety, and they are not targeted enough to fundamentally solve the safety evacuation. , smoke and smoke and other major safety issues. At present, when assessing the fire safety design of subways, these codes cannot be used as the only evaluation basis. The characteristics of subways and the urgency of fire prevention determine that subways should have higher safety performance and standards.

( II ) Difficulty in fire inspection and supervision

The large-scale metro project, complex project, and long construction period make it difficult to audit and supervise.

1 . Fire inspection and supervision pressure

Subway engineering is a livelihood project that is highly valued by the government and has received great attention from the general public. In the aspect of fire safety in the subway, the fire protection design is the first firewall and has an important position in it. Some local governments and departments have deviations in the concept of fire safety. The opening of the subway as a political performance project is regarded as a political task, which emphasizes the development of light security. There are even some governments that use administrative means to intervene in the fire inspection and supervision work. There are some lines that have not been approved for construction. construction, no acceptance of the phenomenon on traffic operations, at the expense of the cost of fire safety, giving the subway seat belt to serious birth risks.

2 . Fire inspection and supervision

The subway project is different from a single building and is a complex system project. It mainly consists of underground railways, stations, control centers, main substations, and vehicle bases. It has a long design cycle, a large amount of works, and most of them require performance. The design of the project and the expert's demonstration have involved many issues and are widely connected. It is extremely difficult and difficult to audit the project.

3 . Inexperienced firefighters

Cities such as Beijing, Shanghai, and Guangzhou have been building early, and subway networks have been established in all directions. In addition, most cities that are building subways are built for the first time. Firemen involved in auditing and supervision are lacking in subway construction. Perceptual knowledge, lack of understanding of the fire safety standards and fire safety technology in the subway, how to strictly enforce the law to carry out audits and supervision work is a difficult problem faced by firefighters.

( III ) The backwardness and aging of existing line facilities

Judging from the current status of domestic subways, the construction of Beijing Metro Lines 1 and 2 was earlier and there was no regulation as a basis ; the Beijing Metro Lines 4 and 5 and the early-built Tianjin, Shanghai, Guangzhou, and Nanjing subways were based on the 1992 edition. The design code for underground railways is the basis ; most of the current operations and construction are based on the 2003 version of the “Design Code for Metros”. Due to the large differences between the old and new regulations, judging from the existing fire control standards, the existing subway line fire facilities are not perfect, and the functions are lacking. It is difficult to meet the requirements. For example, there are control logic errors in the automatic fire alarm system, insufficient host capacity, and detectors. High false alarm rates, poor reliability, and incompatibility between new and old systems. Some lines that have operated for many years suffer from serious aging of existing equipment, and long-time operation of electrical equipment such as fans, air conditioners, lighting, escalators, and control systems. Some cables have no fire protection, no fire-retardant treatment, messy installation, and serious electrical fire hazards. There are problems with the ventilation system of some old subway lines, and there is a problem that the ventilation system is converted to a smoke exhaust system with insufficient air flow and the fan does not tolerate temperatures. There are also stations on the ground where the wind pavilion is blocked and seriously affected the ability to supply smoke during the fire.

( 4 ) Incomplete fire separation measures

The existing stations will be divided into a fire zone according to the specifications of the public areas and stations of the station hall, and be separated from the station management area, shops within the station, and adjacent property development rooms. In order to meet the functional requirements of the platforms and the station halls, a large number of fire shutters were installed. However, with the increasing number of subway traffic, the public areas of some multi-line transfer stations are as large as thousands or even tens of thousands of square meters. Such a large fire protection zone is extremely unreasonable. In practical use, fire shutters have problems such as poor fireproof and smoke prevention, and low reliability ; some pipelines do not carry out effective fireproof blocking through fireproof partitions, which can easily cause the expansion and spread of smoke and fire.

( E ) Difficulties in safe evacuation

In the event of a fire in the subway, the passengers on the trains entering the station and the waiting persons on the platform shall all be evacuated from the platform to the safe area within 6 minutes . Due to the influence of various factors, the difficulty of evacuating train passengers and waiting passengers on the platform mainly manifests in the following aspects :

1 . Large staff flow

As an important tool for public transportation, the subway is densely populated and highly mobile. The daily average passenger flow of Beijing Metro has exceeded 10 million, and the average daily single-line passenger traffic of some lines exceeds 1 million. It has exceeded the peak flow of long-term design, and the congestion of the station is very serious. In the event of a fire, the passenger flow will stagnate at the station floor and it will be difficult to organize the evacuation of personnel.

2 . Long evacuation routes and complicated evacuation

If there is a fire at the platform, waiting passengers on the platform must go from the platform to the public area of ​​the station hall via a staircase or escalator, then pass through the ticket gate to the exit of the station hall, and then pass the stairs or escalator to the ground exit. Such a route is not so close. In some large transfer stations, the distance between evacuation passages is longer, and there is also a phenomenon in which there is no distinction between online passengers and transfer passengers leading to cross-counterflow. In addition, due to the deepening of underground commercial development, as well as the geological hydrology of the built city, etc., the depth of the subway station is increasing. At present, the station with the largest number of transfer lines in China is Shanghai Century Avenue Station, which is the largest four-line and three-level transfer station in China . The largest one is the Chongqing Red Land Station, with a depth of 60 m , from the ground to the station hall. There are 354 steps. With the continuous development of subway construction, these records will be constantly refreshed in the future. Long evacuation routes and complex evacuation relationships have brought more severe challenges to subway stations.

3 . The evacuation channel is limited and there are hidden dangers in the evacuation process

In the event of a fire in the subway, personnel will gather at the stairs and escalators, entrances, ticket gates and other nodes, and congestion will easily occur. Especially at the ticket gates and fences used for diversion guidance, personnel can be severely affected. In addition, some stations do not have platform screen doors, which will lead to serious hidden dangers in the evacuation process. Only the first half of 2015, Beijing has occurred eight passenger rail or fall of Tiaogui

Emergencies. In the event of a fire, the flustering and crowding of personnel will increase the probability of a rail-tracking event. It may cause people to fall or touch the third rail and get an electric shock. In the setting of barrier-free elevators, there are some problems such as the absence of stations or location, lack of signage, and the inability to self-open due to passing through the toll area to non-charging areas, which has brought great hidden dangers to the evacuation of disabled persons.

( 6 ) Business Development Brings Fire Hidden Trouble

There are many investments in the early construction of the subway, and the cost of operation and maintenance is high. It is difficult to make up for the costs simply by relying on ticketing revenues. Metros in most cities are at a loss, and more and more cities are introducing commercial development in the subway. These commercial developments include superstructures, station shops, and adjacent property development. The commercial development within the station increases the fire load in the subway station and the possibility of fire, occupying a limited evacuation space, causing greater danger to personnel and increasing the difficulty of evacuation and firefighting and rescue. The increase in the connection between the metro station and the development of adjacent properties has undermined the integrity of the fire zone. In the event of a fire, due to mutual contact and inaccurate reporting, it is easy to cause the spread of fire . With the increase of openings, the evacuation route becomes more complicated, and the subway and adjacent property flow will interfere with each other, which is not conducive to evacuation. There are a large number of advertising carriers such as light boxes and display boards in stations, stations, entrances and exits, tunnels, and carriages of subways, which also increase the potential fire risk of the subway. Excessive commercial development has created a threat to fire safety. Subway operators should strengthen fire safety assessments and conduct commercial development on the premise of ensuring fire safety.

Second, to strengthen the subway fire safety recommendations

( I ) Formulate, revise and improve relevant subway standards

The incomplete standards and regulations for subway fires have restricted the development of subway firefighting work. In the aspect of subway construction, there is no need for a professional and meticulous “Code for Fire Protection Design for Subways” as the basis for evaluation. The focus should be on scientifically reasonable aspects such as fire zoning, fire separation, safety evacuation, and smoke control systems for underground stations and underground sections. Regulations, while it is still in the process of development, can not keep up with the pace of urban subway development. In the areas of subway vehicles, construction, renovation, and operation and management, relevant departments also need to pay close attention to summarizing the experiences and lessons of fire prevention practices for subway lines built at home and abroad, absorb the advanced research results of subway fire safety, and formulate relevant regulations for subways in a timely manner. Fire safety provides effective guidance.

( II ) Countermeasures for fire inspection and supervision

The fire department should strengthen communication and exchange with government departments, do a good job in propaganda work for subway fire safety, earnestly achieve safety first, take people as the center, and increase the attention of leaders at all levels to the safety of subway fires. The fire department under construction or waiting to be built in a subway city must actively learn the experience and lessons learned from the fire inspection and supervision of subways in the existing metropolitan cities, understand the key points and difficulties in the supervision and supervision of subway fires, and strengthen the perception of sensibility for the subway project. The audit, inspection and acceptance, and the post-fire supervision and management work are ready. During the review, it is necessary to pay attention to grasping the relationship between the whole and the local, grasp the main contradiction, grasp the overall fire design plan, decentralize the examination of all special firefighting designs, and focus on reviewing the fire zoning, fire separation, and safety passages involving life safety of personnel. In the course of auditing and acceptance, strict checks and strict audits are conducted to ensure that no hidden troubles are left behind.

( III ) Speeding up the fire reconstruction of old lines

Accelerating the fire-fighting transformation of old lines and improving the subway fire-fighting system are of great significance for improving the operational reliability and safety of the subway. The firefighting renovation of old lines is as follows:

(1) To be old

The fire problems existing on the line are touched and visited to clarify the scope of rectification ;

(2) In accordance with relevant regulations and requirements, combined with the actual conditions of subway lines, stations, etc., determine the transformation objectives, do a good job of overall design, and consider the compatibility of new and old systems when designing ;

(3) Do a good job in the construction process

Quantity inspection and acceptance after the completion of the transformation to ensure that hidden dangers are eliminated and the requirements are met. In the construction process, we must do a good job of fire supervision and management at the construction site. Fire-fighting reconstruction of opened lines often cannot affect the normal operation of the subway. Due to the decommissioning of some facilities in the process of reconstruction, the safety risks of vehicles, passengers, and construction workers will be extremely high. Therefore, transitional equipment, subway stations, and construction units should be adopted as much as possible. The firefighting forces must make corresponding emergency plans and organize drills to ensure the fire safety of the construction process.

( d ) Take effective fire separation

Stations and other locations, station halls and neighboring property developments are often equipped with fire shutters as a fire barrier. In order to meet fire protection requirements, the width and ratio of fire curtains should be limited. Roads for evacuation of passengers shall not be provided with fire shutters. If there are difficulties, Class A fire doors shall be installed on both sides of the shutters. The connecting channel between the station and the adjacent property shall be provided with two roller blinds, which shall be separately controlled by the station and the property party, or protection nozzles may be provided at stations and commercial junctions to prevent the fire from spreading and expanding. The pipelines that pass through the fireproof partitions such as floors, walls, and fire shutters shall be well sealed and filled with fire to prevent the spread of fire and smoke.

( five ) ensure the safety of personnel evacuation

The evacuation system design of the subway is directly related to the life safety of the people in the fire. In the subway design stage, full consideration should be given to the long-term peak passenger flow, and the effective evacuation width and the number of safe exits should be designed. When the transfer channel catches fire, it cannot be used as an evacuation channel. It is necessary to rationally plan and distinguish the transfer channel and the evacuation channel so as to avoid cross-counterflow of the human flow. When the entrance and exit passage exceeds 100 m , a safety exit through the ground shall be added in the middle of the passage or measures shall be taken to meet the safety evacuation requirements. Escalators in subways should be used for evacuation in case of fire. Escalators with the same direction of evacuation should maintain normal operation in case of fire. Escalators facing away from the direction of evacuation should be able to stop and operate in reverse direction and issue warnings to passengers. The ticket gates and fences should be able to open in the event of a fire and must not affect the safe evacuation of personnel. In order to ensure the safety of evacuation personnel, screen doors should be installed on both sides of the platform. The shielded door shall be powered by the primary load, ensure normal operation in case of fire, and open with the emergency button. In the construction of subway stations, disabled facilities such as barrier-free elevators should be constructed synchronously. The location should be designed reasonably and there should be obvious signs ; the old station should be remodeled and installed with barrier-free elevators ; the unqualified stations can be equipped with stair lifts and other facilities. Disabled people are evacuated. Stations should make actual plans for safety evacuation, organize drills, identify problems, and constantly modify and improve plans.

( F ) Rational Development of Metro Commercial

The main function of the subway is transportation. Under the premise of guaranteeing the safe operation of the subway, reasonable development of business is worth advocating. To strictly examine the commercial facilities set up in subway stations, it is forbidden to install shops, advertisements, and service facilities that affect evacuation. The shops in the subway station should be used as an independent fireproof unit, with good fireproof separation between the station hall and the fire extinguishing facilities, mechanical smoke exhaust and fire detectors. Stores in subway stations are prohibited from selling dangerous substances such as flammable and explosive substances. The safety exits of subway stations and adjacent properties should be set separately, and mutual access channels must not be mutually safe exits. It is necessary to do a good job of separating the fire prevention of subway stations and commerce, strengthen information exchange and linkage control, and reduce the spread of fire and smoke during fires.

Third, the conclusion

With the rapid development of the urban economy, more and more people have to solve the problem of travel, the construction of the subway has reached its climax, but the fire in the subway and the serious damage caused by the fire is equally worrying. There are still many problems in China's subway fire protection. We must adhere to prevention and do a good job in subway design, audit, construction, acceptance, operation and daily supervision and inspection, eliminate underground fire hazards, and ensure safe subway operations.

This article "Journal of the People's Armed Police Academy" 2015 12th issue.