On June 14th, China Construction Transportation's "Foundation Pit Air Film" Construction Technology and Quality Observation Exchange Meeting was held in the Xinxing Shengwei Reform Project. The foundation pit air film technology has effectively improved the conditions of the construction site, created a new application of dust prevention and noise reduction in construction sites, and solved a series of problems such as construction dust and noise from the source.
The foundation pit project is fully enclosed construction site
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Foundation pit air film is a new green construction process that has both dustproof, noise reduction, energy saving, fire prevention and intelligence. There is no need for any beams and columns, which can create a larger construction space with full headroom. The air film is equipped with an intelligent control system, an intelligent detection and alarm system, a fire protection system, and a ventilation system to ensure safe construction.
The foundation pit gas film of the Xinxing Sheng Dangerous Reform Project has set a record of "one of the best" and "one first" of the foundation pit gas film in the country: the most complex foundation pit gas film in the country and the first double foundation pit gas film in the country.
The Xinxingsheng Dangerous Reform Project is located 3km west of Tiananmen Square in the core area of Beijing, close to Chang'an Avenue, the most important arterial road in Beijing within the Second Ring Road. The overall planning is positioned on the basis of satisfying the key functional planning of the core area, conforming to the impact of the climate economy on the national strategy, improving the standard of ecological civilization construction, and seizing the opportunity of carbon neutrality to build a green, low-carbon and recyclable technology demonstration park.
The project sets up two foundation pit air films, which are applied to the foundation pit of the 5# building and the 6# building respectively, covering an area of about 13,400 square meters. Among them, the 6# building air film, with a height of 18m, a length of 55m, a width of 59m, a total area of 3146 square meters, and 2 vehicle access channels; The height of the air film in the 5# building is 25m, the length is 144m, the width is 74m, the total area is 10294 square meters, and there are 3 vehicle access channels.
Overview of air film applications
1. The air film adopts a new type of environmentally friendly, fireproof, strong acid and corrosion-resistant PVDF building membrane. The overall shape is an arched surface, which is beautiful and generous, and the color is gray as the main color to avoid light pollution caused by strong sunlight in summer. The high-performance air membrane building can withstand strong winds, rain and snow in bad weather, and the protective coating is resistant to high temperatures and has superior flame retardant properties. It is equipped with fire protection, exhaust, sprinkler and dust reduction systems and a fully intelligent monitoring system to provide a strong guarantee for the safety of the foundation pit.
2. Foundation pit air film technology, as a large-span and intelligent building technology, realizes the full use of building space by using the pressure difference between the inside and outside of the air film. The application of this technology not only improves construction efficiency, but also plays a significant role in environmental protection.
3. The foundation pit gas membrane adopts longitudinal and horizontal cable nets, anisotropic membranes, the elastic modulus of the meridional membrane is 900MPa, the Poisson's ratio is 0.3, and the strength standard value is 7500N/5cm; The elastic modulus of the weft film is 600MPa, the Poisson's ratio is 0.2, and the strength standard value is 7000N/5cm. The shear modulus is 10MPa, and the thickness of the film is 1.0mm, which is the P class film. The longitudinal and horizontal cables are arranged on the membrane surface to work together with the membrane to make the membrane surface more uniform and beneficial, and the elastic modulus of the cable is 130GPa. The steel cable is made of 6x36WS+IWR-1960MPa, and the steel cable specification is φ18PE22. The cable net anchorage uses the existing crown beam and is fixed with M30 chemical anchor bolts and pull rings.
4. Air dome access door system
(1) Personnel access channels; Personnel in and out of the passage for the special channel, the passage door using airtight revolving door 2200mm (width) × 2400mm (height), personnel in and out of the door to ensure air tightness, airtight revolving door, the door body using stainless steel frame structure, the wing of the door using stainless steel outer frame, the internal configuration of laminated tempered glass.
(2) Car access
The foundation pit air film is provided with a car channel, the channel adopts a steel structure, and the closed door at both ends of the channel adopts a hard fast rolling door, the door has a low failure rate, fast opening speed, and the vehicle pass rate is high per unit time, and the door leaf is 5.0m wide * 4.5m high, which is divided into two internal and external doors. After the completion of the construction of the steel structure of the automobile channel, the air film unit shall carry out the construction related to the closure of the airtight opening. The outside and inside of the passage are provided with vehicle sensing device and linkage device, when the vehicle drives to the channel and reaches the specified distance, the relevant side of the passage door automatically opens, until the vehicle drives into the vehicle sensing area in the passage, the system can automatically close the passage door, when the passage door is completely closed, the linkage device of the passage door starts, automatically opens another passage door, after the vehicle drives out of its passage, the passage door is automatically closed. The car access door needs to be installed with an interlock device, that is, the two doors cannot be opened at the same time, only one can be closed and one open.
5. Air film air supply equipment system
The maximum pressure inside the air film can be maintained at 200~240Pa. The fan is uniformly arranged on the side of the foundation pit air film. The intelligent control system controls the operation of the fan and the power frequency fan by adjusting the frequency conversion, and inflates and pressurizes the air film to maintain the pressure difference between the inside and outside of the air film. In order to prevent the internal pressure of the air film from exceeding the control range, an overpressure relief valve is set at the same time, which is shared with the exhaust valve. If there is abnormal conditions such as abnormal fan equipment and pressure loss in the membrane, the intelligent control system can detect and automatically start the backup energy and backup equipment, and send a short message to the administrator's mobile phone and the control room for sound and light alarm.
6. Air film electrical system
The electrical system of the air film design of this project mainly includes the primary wiring and equipment layout of the air film electrical, the electrical control system (including the car door system), the acceptance and implementation of the standby diesel generator system.
7. Air film intelligent control system
The intelligent control system (PLC) is the control core of the air film facility, which collects data from various indoor and outdoor sensors (such as indoor air pressure, indoor temperature and humidity sensors, outdoor wind speed sensors, outdoor rain and snow sensors, etc.), transmits the data back to the intelligent electromechanical control system in real time, and automatically adjusts the ventilation volume. Intelligent control of the coordinated operation of various equipment systems to achieve humanized operation and management, so as to achieve the safety of air film facilities, 24-hour unmanned monitoring, fully automatic operation, and remote operation and monitoring, to ensure safe production, energy conservation and environmental protection.
8. Air film intelligent detection and alarm system
This project is equipped with environmental monitoring and other sensors inside the foundation pit gas film. Make an exhaust hole at the top or bottom of the air film and install an automatic exhaust valve, the exhaust valve will automatically open after reaching the set value, and the internal harmful gases and dust will be automatically discharged to the outside of the site through the exhaust hole. (B6# building air film is equipped with 1 indoor temperature and humidity sensor, 1 wind speed sensor, indoor and outdoor pressure difference sensor 2 for monitoring the internal environment and temperature and humidity values, these sensors are monitored in real time, and the data is processed by the CPU, according to the set program to intelligently control the fresh air, ventilation, exhaust and other devices to work efficiently to ensure the safety of the air film.) ）
The significance of the application of air film
1. The construction is not affected by bad weather, and workers can work normally in windy, hazy and blizzard weather, and can strive to shorten the construction period, so that the project can be put into use in advance, bringing a good living environment and convenient transportation to the surrounding residents.
2. In terms of environmental governance: First of all, the dustproof performance of foundation pit air film technology is particularly prominent. Due to the pressure difference in the air film, it can effectively block the entry of external dust, significantly reduce the overflow of dust, so as to effectively protect the environment of the construction site, according to the calculation and evaluation, the air film method can reduce the emission of harmful gases and coarse particles by more than 90%.
Secondly, the technology also has good noise reduction performance. The north side of the project is adjacent to Zhonghai Triumph Community, the east side is close to Xicheng District Government, the west side is adjacent to Beijing No. 8 Middle School, and the south side is across the road from the head office of Industrial and Commercial Bank of China. Through the air film technology, the on-site construction noise can be isolated, the impact of construction on the surrounding residents can be effectively reduced, the civilization of the construction can be improved, and the living environment level of the city can be further improved.
3. Foundation pit air film technology also has the characteristics of energy saving and fire prevention. Its design makes full use of natural light to effectively reduce energy consumption, while the air film material has good fire performance to provide safety for the construction site.
4. It is worth mentioning that the foundation pit air film technology is also integrated into the intelligent management concept. Through the intelligent control system, the environmental parameters in the air film can be monitored in real time, and the real-time monitoring and adjustment of the construction site environment can be realized, so as to further improve the construction efficiency and management level.
5. The temperature inside the film is about 10°C higher than the temperature outside the film, which is conducive to winter construction and can reduce the impact of low temperature on the construction of workers. During summer construction, workers can avoid direct sunlight, and the air film can open all the air ducts to facilitate air circulation in the membrane.
6. The foundation pit air film effectively reduces the number of coverage of the bare site, before the air film is not covered, because the foundation pit excavation has not started construction, almost all the construction site needs to be covered, which increases the input of manpower and material resources. After the foundation pit is covered with an air film, the work is significantly reduced, saving manpower and material resources.
7. The overall shape of the air film is an arched curved surface, which is beautiful and generous, and is not obtrusive when placed in the site, so as to ensure that the on-site construction site is clean and tidy, and the appearance is more coordinated and upright. The color of the air film is gray as the main color to avoid light pollution caused by strong sunlight in summer.
After the foundation pit gas film is put into use, it can effectively reduce the emission of harmful gases and coarse particles, and at the same time reduce the noise generated by the internal operation of the gas film, minimize the impact of the construction process on the surrounding residents, and achieve "zero complaints" from the surrounding people. It also reduces the delay and resource consumption caused by bad weather, repeated coverage, etc., and is expected to save the construction period by more than six months. It has truly realized the coordination and unity of "grasping progress" and "not disturbing the people", and solved the problem of "Ande and Quanquan Law". Improve the degree of construction civilization and further improve the level of the city's living environment.
Originated from 丨China Construction Transportation Railway Company