Study On Risk Evaluation And Control Technology Of Shielding Construction Of Beijing Underground

Shield construction process is one technique commonly used municipal engineering, shield method of construction using a special tool to shield machine. Shield machine is based on the construction object "tailor-made", the shield machine manufacturing is based on the object, called the construction environment, it is the basic geology, engineering geology, hydrogeology, geomorphology, surface buildings and underground pipelines, and structures and other features combined. It can be seen, if you do not study in detail the construction environment, you can not create adaptable shield machine, let alone carried out smoothly shield construction. Factors in the construction environment, the basic geological and engineering geological characteristics are the most important,Because they are the shield machine selection and the use of shield construction technology of the most important prerequisite. In practice, the study of geological features is often neglected. As everyone knows, the shield construction technology is all closely related with the geological features, especially the complex formation of the shield construction. Construction of shield machine and the shield is a huge construction of production systems, including horizontal and vertical transportation, mechanical and electrical equipment installation and operation, real-time measurement monitoring, water-proof sealing, tube sheet transportation and assembling, grouting and a series of complex simultaneous process involving the safety ofMan, machine and environment, all systems require the latest security theory provides guidance and services. In this paper, Beijing Subway Construction geological model, the settlement model, shield-parameter model studies, have greatly enriched the theory of security shield construction to promote the theory of security technology and security developments in the field of construction in the metro comparison, the Shield Construction structure has a clear advantage, reflected in the following areas:(1) Less environmental impact. In addition to originating stations or construction of wells, the range of underground construction operations are carried out, dust, noise, vibration caused by a smaller environmental hazards;(2) Underground shield construction, does not affect the ground level road traffic;(3) When the tunnel across the river, rail or other structure, the impact controllable;(4) A high degree of mechanization. Shield forward, out of slag, lining and other major assembly processes are completed on cycle shield system, the construction with less labor, productivity is higher;(5) The construction of the production from wind and rain shield and other weather conditions impact; by the engineering geology little effect on hydro-geological conditions, with good technical and economic superiority.However, our relatively short history of rail transportation, construction, lack of experience, shield, there are still some problems as follows:(1) The Shield construction safety technology and safety management was low. China has not yet established an independent shield machine manufacturing industries, shield machines rely mainly on imports or imported from different countries, facilities, equipment for domestic assembly and localization of the degree of independent intellectual property rights is low.(2) Subway construction complex environment. Subway Construction sites are mostly located in the dense, peripheral complex, across a variety of buildings, railways, rivers, bridges and other operations have become increasingly frequent, and because the construction of more nodes, the construction units of different management philosophy, different levels, giving subway Construction on the project and the future operation and management leave should not be ignored and security risks, only in 2006 Beijing Metro Line shield construction on the three major cave-in accident, the serious impact on people's lives and property, resulting in the construction and operation of different social benefits.(3) The late start of our national security science, security, technology development is lagging behind. Subway Construction risk of lack of research depth, most of the analytical tools, research methods continue to rely on learning or imitation of other industries, there is no theory of the formation of shield system's security and safety control technology.Region is located in Beijing in the Yongding River flood alluvial fan in the upper part of Quaternary loose soil and sand and gravel all over the city. Its geological deposits of the "phase change" is clear, coarse grain sediments west to east will soon fade as the small particles sediment; a single sand and gravel west to east gradient of clay, and soon each layer of fine sand multi-state. Within the Fifth Ring Road and the rings surrounding the extent of about 800km2 use of shield construction, it will encounter the following types of characteristics of highly viscid Beijing strata of silt, silty clay and sandy soil and sand and gravel. Western Sand and Gravel will be primarily based,Such as the Marco Polo Bridge area and Shijingshan-Shougang area, its well-graded sand and gravel, the largest particles of up to 40cm or more. The south or south-west, north or north-west, will encounter a small amount of clay of the Sand and Gravel and the whole cross-section of Sand and Gravel, these strata of sand rate is about between 25%-40%, in the east, mainly clay or sandy soil.Beijing's underground water strata or rather shallow groundwater is generally the Department of Quaternary strata in the groundwater. Usually considered to comprise three kinds of water, that is, perched water, diving and shallow confined water. Another, landscape, river and lake water leakage as well as urban water and sewer leakage of water, according to their type of occurrence can also be included in the above three kinds of water, of course, its should be a special kind of urban water. According to the Beijing Municipal Government adviser Professor Hou Jingyan water resources research, water-bearing area of Beijing can be broadly divided into 5 sections. I zone water-rich region:mainly distributed in the Beijing central and western regions, namely, College Road, Wudaokou, Purple Bamboo, Fuchengmen, Temple of Heaven Park, west of theAn area of about 135 km2. The average aquifer thickness of 13m, permeability coefficient of 60～150m/d, an average hydraulic gradient of 0.2%;Ⅱarea water-rich region:mainly distributed in the urban heart of the National Palace Museum as the center showed the distribution of Y-shaped north-south strip.28 secondary schools in the vicinity west of Tiananmen Square in which the aquifer permeability coefficient of 40～80m/d, an average hydraulic gradient of 0.15%;Ⅲarea middle water-rich region:roughly divided into two, the first piece east of the eastern Xibahe, East City of Victoria west of the zone; another piece of Xibahe, Beixinqiao area.Ⅲtotal area of about 61km. Its layered obviously, with an average permeability coefficient of 30～60m/d; IV District weak water-rich region:mainly distributed in the Anzhen bridge, the sun, west of Gongzhufen official close to the total area of about 20 km2.The average permeability coefficient of 20～40m/d; V-deficient water area:This area is basically non-aquifer, distribution is more mixed.From the above we can see that the Beijing area geological and hydrological conditions are distinctly different from the characteristics of other cities, using shield technology during the construction, will have to address its own characteristics, to take corresponding countermeasures, selection of corresponding shield machine and take of appropriate technical measures. For example, a typical in Beijing Sand and Gravel, it should select the appropriate shield Cutter, in order to increase Cutter life, reduce consumption and for Segment Segment caused by construction costs and construction risks.In this paper, Beijing Metro Line 4# standard, for example, in Beijing, the water level of the engineering geology geological conditions, surrounding environment, shield the construction process, work area and other relevant characteristics of hazards and provide hazard identification list for the construction of enterprise systems, complete control of potential safety problems, develop sound security measures, in order to provide adequate safety assessment of this next detailed basis; of Beijing Subway Construction risk analysis and risk assessment to guide in Beijing shield construction safety in production and safety management; to shield construction The shield construction to create a scientific risk-management procedures and to develop projects for enterprise shield construction risk assessment system, Shield construction project for the enterprise risk management, standardization and procedural basis for the provision of appropriate and reference standards; the establishment of subway construction in Beijing geological model, control model parameters, surface subsidence prediction model and the risk prediction model, in order to provide a theoretical basis for the security control technology; to shield through the existing building (structure) building materials, river, bridges, railways and other control technology research, to provide scientific, security, shield construction safety recommendations. In this paper, the investigation in Beijing shield construction engineering geology hydrogeology, as well as surface and subsurface environment, the environment in Beijing shield the complexity of the construction carried out a detailed analysis of study. Beijing Metro Line 4 with standard engineering practice, the Beijing Subway Construction hazard area was analyzed and determined that shield and out of holes, shield beneath the process of high-rise buildings, shield beneath the process of river, under the shield to wear during the course of the road as well as shield beneath underground pipelines as a major risk source of these major risk source of the risk of accidents that may occur are analyzed.In this paper, a pre-risk analysis method, the early stages of shield construction materials, devices and energy control may occur when the risk categories, conditions and possible consequences for the broad macro-analysis to determine their risk level, in order to prevent similar risk loss of control of harmful factors leading to accidents.Based on the R=P×C classification method that combines qualitative and quantitative risk analysis methods, combined with the Beijing area engineering geology, hydrogeology and surface underground environment, and the Beijing Metro Line project they saw Road Station-Beijing South Railway Station range of the specific circumstances of shield construction selected for the construction of the 22 risk source as a major risk, the works R=P×C rated risk assessment.This paper selected earth pressure balance technology as the main type of analysis to establish a tunneling process of the various parameter models. Have the following main parameters:soil storage pressure, the advancing speed, the overall thrust, the amount of waste pile, knives plate speed and torque, grouting pressure and grouting volume, foam, slurry injection rate, in order to shield construction provides a certain theoretical risk control foundation.In this paper, engineering practice, the construction of the shield lines, soil subsidence monitoring methods, and conducted a detailed analysis of settlement prediction, and control the proposed settlement of soil control technology.In this paper, the specific stratum in Beijing shield machine selection analysis, and for the Beijing Sand and Gravel, the shield construction tool wear problem were discussed; selection of examples under the knife and put forward the amount of tool wear and the tunneling distance regression relationship.For the large-diameter shield out of its hole when the security issues out of its hole on the shield section to evaluate the stability of the soil, Shield Construction in Beijing discussed the reinforcement of soil suitable for construction method proposed shield Houtu body compressive reinforcement, shear strength and the overall stability of the calculation method, combined with engineering examples were calculated.This study object is in Beijing Sand and Gravel shield construction risks, has certain limitations. According to the different formation conditions, the construction of the risk shield is also different, their control measures is very different. Therefore, the need to collect a large number of construction materials, the situation in different regions of the strata a risk analysis model to analyze their risks, for a variety of geological conditions under the prevention and control risk shield construction to provide guidance.The construction period of risk analysis should include the construction organization design and engineering phase of the construction process of risk analysis, risk analysis. This article assumes that the selection and design of the program is fully applicable only to the construction process of risk analysis. Practical in the engineering design phase will need to consider the size of the risks of various options, choose the least risk, lowest cost solution.In this paper, risk analysis models are qualitative or semi-quantitative. Clearly the credibility of the results of semi-quantitative than qualitative results greatly enhanced, but still there are human factors, and expectations of the results is still a certain gap. Therefore, how to conduct quantitative analysis of the real risk needs to be done in-depth thinking and research.This risk analysis process, the main core objectives of security analysis, economic indicators, research priorities have not been unable to achieve the technical, environmental and economic balance of the three. Further analysis of the risk of economic loss arising from the insured the sum insured can be predicted, can help the owners as much as possible to ensure the safety of circumstances, to save the cost of the risk of handling or transfer.Risk analysis as a method of underground engineering is being widely watched. With the large-scale underground project investment in the future subject of diversification, risk analysis and risk control is bound to more and more attention. The study of the issue is not only has theoretical significance, but also to avoid risks, to guide the actual works.Construction subject to the Shield security technology, security management, security, education, research, construction safety management level of the shield made of evaluation findings to enable enterprises to not only understand in the process of shield construction elements and its possible risks the risk of causing accidents, but also specifically how to improve the security situation in the fields of engineering for enterprise production safety shield macro-control to provide basic, objective data and system control technologies to reduce casualties and environmental destruction, to effectively control construction costs and construction schedules, improve enterprise economic returns and social benefits.Interval according to the geological condition of the tunnel and the surrounding environmental conditions, in order to ensure the stability of the excavation face and effective control of surface subsidence along the constructs and to ensure the safety, construction management, the main choice of seven indicators to carry out tunneling control management: Dokura pressure; forward velocity; general thrust; Dump volume; cutter speed and torque; grouting pressure and volume; foam, slurry injection rate, which Dokura pressure is a major control targets.China is the tunnel construction, the world powers, especially in recent years, major cities began construction of the MTR, the subway is now slowly entering the height of the building. Far as in Beijing has been initially formed the basic skeleton of rail transportation, according to the 2020 Beijing subway line is expected to become the world's total length of the longest city. Development of the MTRC is easing the traffic problems in major cities to facilitate the people's lives. But the subway construction costs are high, risks are great, the event of a dangerous situation, the cost is even straighter up. Thus, for subway construction in the process of risk analysis and control has become an important research direction.Shield is an important link in the subway construction, but also dangerous to multiple stages. The present report systematically and comprehensively studied in Beijing shield construction of the various risk factors and to build models, combined with engineering practice, put forward a feasible control measures. However, due to the level and the limited time available, the report is in some respects, has made some tentative explorations, in many ways remains to be further study.(1) The object of study is in Beijing Sand and Gravel shield construction risks, has certain limitations. According to the different formation conditions, the construction of the risk shield is also different, their control measures is very different. Therefore, the need to collect a large number of construction materials, the situation in different regions of the strata a risk analysis model to analyze their risks, for a variety of geological conditions under the prevention and control risk shield construction to provide guidance.(2) The construction period of risk analysis should include the construction organization design phase of the construction process of risk analysis and risk analysis. The report assumes that the program selection and design of fully applicable only to the construction process of risk analysis. Practical in the engineering design phase will need to consider the size of the risks of various options, choose the least risk, lowest cost solution.(3) In this paper, the risk analysis models are qualitative or semi-quantitative. Clearly the credibility of the results of semi-quantitative than qualitative results greatly enhanced, but still there are human factors, and expectations of the results is still a certain gap. Therefore, how to conduct quantitative analysis of the real risk needs to be done in-depth thinking and research.(4) To conduct risk analysis is an important aim is to reduce costs. The process of conducting risk analysis of this report, the main core objectives of security analysis, rather than a focus on economic indicators, and can not achieve the technical, environmental and economic balance of the three. Further analysis of the risk of economic loss arising from the insured the sum insured can be predicted, can help the owners as much as possible to ensure the safety of circumstances, to save the cost of the risk of handling or transfer.(5) Risk analysis as a method of underground engineering is being widely watched. With the large-scale underground project investment in the future subject of diversification, risk analysis and risk control is bound to more and more attention. The study of the issue is not only has theoretical significance, but also to avoid risks, to guide the actual works.