Since the beginning of the new century, the rapid expansion of urban population in China has caused a series of problems. In particular, traffic congestion has seriously hindered people's travel. In order to alleviate the traffic pressure, many cities have started subway construction. However, due to the immature construction technology and experience, as well as the lack of effective monitoring of the construction process, construction safety accidents have occurred from time to time, which has brought huge loss of life and property to construction workers and people. Therefore, it is of great practical significance to effectively monitor the subway construction process.
Analysis of the influence of urban subway construction on the surrounding environment
There are many high-rise buildings in modern big cities, and the traffic roads and underground pipelines are complicated. Earthwork blasting, underground tunnel excavation and load-bearing arch hole construction will inevitably affect the surrounding environment. Once there are loopholes in the detection of these buildings, it may lead to a series of major safety accidents such as ground cracking or settlement, hole collapse, building collapse, water supply, gas supply, power supply and other pipeline rupture, which seriously threatens the life safety of construction workers and residents. The impact of subway construction on the surrounding environment is analyzed as follows.
1. 1 Analysis of the influence of earthwork blasting on the surrounding environment
Blasting technology will be used in the excavation stage and tunnel excavation construction of urban subway construction site. We know that in engineering blasting, explosives are usually placed in relatively closed boreholes or holes, which will indirectly increase the blasting power. The shock wave and vibration with higher energy will have a greater impact on the surrounding buildings or the ground, and the cavities generated by blasting will also greatly change the bearing structure of the construction stratum. Therefore, if the blasting monitoring work is not in place, it may cause large ground subsidence, buildings collapse due to earthquake or foundation damage, and major safety accidents such as water supply and gas supply pipeline explosion.
1.2 Influence of underground tunnel excavation on surrounding environment
Subway construction must dig underground holes extending in all directions to accommodate subgrade, vehicles, stations and other facilities, and the amount of earthwork excavated (in many cases, engineering blasting will still be used) is very large. In the process of construction, the original buildings, roads, overpasses and other complete foundation load-bearing structures above the holes will be destroyed, resulting in the imbalance of the original uniform stress points of the superstructure. If there is no construction monitoring or there are loopholes in the monitoring work, the excavated holes are likely to exceed the maximum damage limit allowed by these load-bearing structures, making the superstructure completely out of balance, thus leading to the consequences of its inclination or even collapse. But also may lead to deviation in the direction of excavation, resulting in a lot of waste of manpower and material resources.
1.3 Influence of load-bearing arch hole construction on surrounding environment
In the process of underground cavern excavation, in order to ensure that there are no holes or minimize the adverse impact on the surrounding environment, load-bearing arch holes are usually built at the same time. Its purpose is to effectively correct the deviation of the balance point of the load-bearing arch hole when the underground load-bearing structures of buildings, roads and overpasses above the hole are destroyed, so as not to make the deviation of the balance point out of control. However, it is difficult to determine the construction radian, toughness and maximum bearing capacity of arch tunnel without the support of corresponding construction (referring to the construction of arch tunnel). Once the completed arch tunnel can't meet the actual requirements, it can't play its due role, and it will also lay a serious safety hazard for the subsequent construction and use of the subway.
The important role of subway construction monitoring in subway construction
The occurrence of the above-mentioned series of safety accidents is directly related to the construction monitoring. Practice has proved that effective monitoring of subway construction can control the influence of the construction process on the surrounding environment to a great extent, greatly reduce the probability of major safety accidents, and optimize and guide the subway construction process through monitoring.
2. 1 The role of monitoring in blasting construction
2. 1. 1 helps to select the appropriate blasting point.
Through the relevant monitoring technology, the stratum structure of the construction site, the trend and distribution of power supply and water supply pipelines in the stratum can be detected before blasting, which provides necessary data for the selection of blasting site. Moreover, the blasting operation can be monitored in the whole process, and once an accident occurs, an alarm can be given in time to remind the construction personnel to take necessary countermeasures quickly.
2. 1.2 is helpful to determine the blasting charge and the best blasting depth.
Explosive quantity and blasting depth have great influence on blasting quality and ground buildings: too much explosive quantity (or shallow blasting depth) leads to high construction quality, but too much damage to ground buildings; If the charge is too small (or the blasting depth is too deep), the blasting purpose will not be achieved. By using relevant monitoring means, necessary data can be collected, the amount of blasting explosives and the best blasting depth can be determined, and the safety range can be delineated, so as not to cause too much impact on the ground buildings.
2.2 The role of monitoring work in tunnel excavation construction
Because digging holes has a great influence on the foundation structure of most cities. Reliable monitoring means can be used to monitor the mechanical structure of stratum and surface at any time during construction, and the information of some problems in construction can be transmitted to the construction command center in time, so that the construction commander can take targeted measures in time. At the same time, it can also monitor some changes of surface buildings caused by construction. In the event of a construction safety accident, people can be evacuated in time to minimize losses.
2.3 the role of monitoring and measurement in the construction of multi-arch tunnel
Effective monitoring of the construction of multi-arch tunnel has the following advantages: (1) monitoring the stress change of multi-arch tunnel in real time, so as to reinforce it in time when the pressure exceeds the bearing limit; (2) It is helpful to determine the radian and toughness of the arch tunnel structure; (3) Collecting the changes of various factors around the construction site can guide the optimization of the construction process.
Shortcomings in Monitoring of Urban Subway Construction in China
3. 1 The monitoring equipment is backward.
The construction of urban subway is extremely complicated, and its construction technology is much higher than other transportation facilities. Therefore, the traditional monitoring equipment has lagged behind the development of subway construction technology and can not meet the requirements of modern urban subway construction. The reason is that the traditional monitoring equipment has great limitations, such as low informatization, low efficiency, small application scope and complicated operation, which can not realize real-time all-weather monitoring, and the monitoring information transmission speed is also very slow, which can not meet the requirements of urban subway monitoring.
3.2 The traffic control department has poor supervision and the monitoring personnel are careless.
Traffic supervision department is the main force to supervise the construction of urban subway. However, due to various reasons, the traffic supervision department did not perform its duties well. Due to poor supervision, many construction units did not carry out necessary monitoring work in order to shorten the construction period and reduce investment. At the same time, some monitoring personnel are not enthusiastic and have incorrect working attitudes. The phenomenon of falsely reporting and concealing monitoring data is everywhere, which makes the construction headquarters unable to understand the real construction situation, which eventually leads to serious construction accidents and incalculable losses to the country.
3.3 The quality of some monitoring personnel is low.
The quality of monitoring personnel will inevitably affect the quality of monitoring work. At present, a large number of monitoring personnel are non-professionals, their professional quality is not up to standard, and their monitoring experience is insufficient, so they can't find out the potential safety hazards in construction in time, can't make reasonable treatment measures for safety problems, and some even can't operate monitoring instruments.
4. Some countermeasures to improve the above shortcomings.
4. 1 Monitoring and testing equipment upgrade.
As the saying goes, if a worker wants to do a good job, he must sharpen his tools first. Do a good job in the monitoring of urban subway construction, without efficient monitoring equipment. Moreover, for the equipment used in the monitoring of urban subway construction, high-tech content can often be exchanged for high work efficiency. Therefore, the construction unit should invest the necessary funds to purchase modern test and detection equipment, put it into actual monitoring, and develop new monitoring means on this basis to meet the requirements of subway construction monitoring in the new stage.
4.2 Traffic supervision departments should strengthen supervision and improve the sense of responsibility of testing personnel.
The following measures can be taken to strengthen the supervision of subway construction inspection: (1) Spot check the monitoring report regularly or irregularly; (2) Assign special personnel to the construction site to supervise and grasp the construction situation in real time; (3) Strictly investigate and deal with construction units or construction personnel who falsely report or conceal the monitoring results. At the same time, the construction safety monitoring responsibility system is implemented, and each monitoring personnel is responsible for the designated construction area. In the event of a safety accident or dereliction of duty, they must bear corresponding responsibilities and accept legal sanctions.
4.3 Effectively improve the quality of monitoring personnel.
This can be achieved by the following measures: (1) introducing professional monitoring talents; (2) Professional skills training for existing personnel; (3) Provide special training on the use of monitoring equipment.
5. Conclusion
Effective monitoring of urban subway construction is the fundamental guarantee to ensure the safety and order of subway construction, and it is also a "reassuring" to alleviate residents' worries about subway construction, so it is necessary to strengthen monitoring of subway construction.
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