1 Overview The main line of Daxing Line of Beijing Rail Transit is 2 1-7km long, which is divided into underground section, transition section and elevated section. Adopt all kinds of ballast beds. On the main line and auxiliary line, the short sleeper monolithic track bed is adopted in the general section of underground line, and the III type damping fastener monolithic track bed, trapezoidal sleeper monolithic track bed and steel spring floating plate monolithic track bed are adopted in the vibration reduction section according to different vibration reduction grades. Viaduct adopts integral ballast bed with bearing platform; The outer line of the yard line and the test line library adopts gravel ballast bed; The whole track bed is used in the warehouse. The variety of ballast bed forms has also caused the diversity of various engineering materials in Daxing line track engineering. Taking fasteners as an example, the underground sections of main line and auxiliary line are generally DT ⅵ 2 elastic separation fasteners; The general section of overhead lines is DT ⅶ 2 elastic split fastener; The universal damping section is a type III damping fastener; The cross section of trapezoidal sleeper is elastic II- 1 fastener; DTⅵ 1 type is used for 60kg/m rail section, and DTⅵ 1 type is used for 50kg/m rail section of station line. DJK5- 1 fasteners for ordinary integral track bed in the depot and the inspection well behind the depot are special gusset fasteners.
According to the procurement method, the materials for the track project of Daxing Line are divided into two categories. The first category is purchased by A, and there are 36 categories in 8 units. The second category is 57 types of materials purchased by the construction unit * * * 16. 2 material management measures 2- 1 urge the construction unit to establish and improve the material quality management system. The quality control of engineering materials is an important part of the engineering quality assurance system of the construction unit and the first level of engineering quality control. Giving full play to the role of the construction unit's own quality assurance system plays a decisive role in ensuring the quality of the project. Therefore, in the track engineering supervision of Daxing Line, the Director's Office attaches great importance to the role of the construction unit's own quality assurance system, and urges the construction unit to establish and improve the material quality assurance system in various ways, so that the construction unit can strengthen investment and management in staffing, system establishment, procedures, methods and means, so that the quality assurance system of the construction unit can operate healthily and play a fundamental role in ensuring the quality of engineering materials. At the beginning of entering the site, the director's office requires the construction unit to report the personnel, division of labor and corresponding responsibilities of the material management department, focusing on checking the qualifications of the testers to ensure that the personnel are in place, the responsibilities are clear, the system runs and the quality is controllable. 2-2 Establish and improve the material supervision and management system and responsibility system of the Director's Office. The sampling inspection, re-inspection and parallel inspection of engineering materials by the supervision unit are effective supplements and supervision to the self-inspection and self-control work of the construction unit, which is an important responsibility of the supervision unit and plays an important role in ensuring the quality of engineering materials. The construction unit must carry out sampling and test work under the supervision (witness) of the supervisor. When the test results of the supervisor are inconsistent with those of the construction unit, the test results provided by the supervisor shall prevail. In view of the actual situation of track engineering in Daxing Line, the Director's Office has formulated detailed supervision rules and defined the procedures and responsibilities of material supervision. The responsibilities, authorities, working methods, steps and means of the chief supervisor, resident supervision team leader, material supervision engineer and site supervision in the material supervision work, as well as the quality requirements of materials and the measures to be taken to ensure the quality are specified in detail. The director's office has set up an entry material test ledger to keep abreast of the material quality at the construction site. The resident supervision team leader is responsible for the statistics and inspection of the materials entering the bid section, and the professional supervision engineer works in strict accordance with the relevant provisions of material supervision. 2-3 Laboratory Management The test (inspection) of track engineering materials can be carried out by the construction unit on site (if there is a laboratory on site) under the supervision of the supervisor, and can also be sampled on site under the supervision of the supervisor and tested by a third-party laboratory. According to the actual situation of track engineering of Daxing Line, all engineering tests and re-inspections are undertaken by third-party laboratories. Therefore, the qualification of engineering laboratory and the accuracy and reliability of test data are very important. First of all, the supervision unit should review the qualification of the test and testing unit. At the same time, when receiving the test report of the inspection unit, the supervision unit should check whether the test data of the materials are up to standard and whether the inspection standards used by the inspection unit are effective, so as to ensure the high standards of the materials used in the project. 2-4 Management of Materials Before the materials plan to enter the site, the material supplier or manufacturer must provide a complete set of material quality certification documents, including ex-factory certificate, quality commitment letter, third-party inspection report provided by the production unit, ex-factory inspection report, quality certificate and raw material entry inspection report, which shall be reviewed by the director's office in conjunction with the construction unit, otherwise they shall not enter the site. 2-5 Material Inspection and Engineering Test Management In view of the narrow subway construction site, it is difficult for construction units to purchase goods in large quantities. For each batch of materials entering the site, the director's office requires the construction unit to stack and store them separately according to the product and model, and confirm whether they have passed the re-inspection. In order to ensure continuous construction, according to the objective conditions of different materials, the director's office divides the materials entering the site into three categories for different degrees of control and inspection. (1) Irreplaceable materials can only be used after passing the inspection (such as all kinds of steel used in ballast beds, etc.). ). (2) For replaceable materials, inspection and construction (such as track connecting parts, etc.) shall be carried out at the same time on the basis that the supplier can provide the material self-inspection certificate and qualified third-party inspection report. ), each batch of used parts should be strictly recorded and randomly sampled for re-inspection. If the first sample does not meet the standard, a second sample can be taken. If it does not meet the standards, the incoming materials will be removed and replaced. (3) Physical tests should be carried out for materials related to engineering use function and safety, and the results are qualified and technically stable, which should be reported to the laboratory for inspection. Inspection and construction should be carried out at the same time, and self-inspection tests should be carried out regularly (such as type test and periodic inspection of rail joint welding, etc.). ) .2-5-1steel For each batch of steel that comes into play, the construction unit is required to keep it in batches and varieties, and fill in the inspection list, indicating the origin, specifications and use parts of the steel. On this basis, the material supervision engineer will check the product certificate, quality guarantee and material test report, and witness the sampling test. Materials that have not been inspected shall not be used in the project; Materials whose quality does not meet the requirements shall be cleared out in time. For example, when the construction unit conducts inspection of the steel produced by Tangshan Iron and Steel Co., Ltd., the supervisors find that there is no nameplate on the site, immediately notify the construction unit to prohibit the use of the steel, and supervise the withdrawal of all the steel. The vast majority of steel bars entering the site must be processed on site before they can be used in the project. Before processing, the construction unit must first make welding specimens, which shall be welded by professional welders. After inspection, steel can be processed and welded. Every 300 joints shall be sampled 1 group for testing, and the sampling shall always be synchronized with the material processing progress. 2-5-2 According to the construction progress and site conditions, the track component construction unit shall submit the material mobilization plan in time. Upon the arrival of the materials, the construction unit shall notify the resident supervision team leader to confirm that the relevant quality certification materials are complete, which are consistent with the physical objects and quantity, and then unload the vehicle without error. Measures such as fire prevention, moistureproof and anticorrosion should be taken for stacking materials to ensure that the materials are in good condition before use. The material supervision engineer shall, jointly with the material engineer of the construction unit, sample different batches of incoming materials according to the principle of one sampling and two sampling, and send them to the third-party inspection unit for a second interview. Only after passing the inspection can it be used in the project, and the unqualified products shall be ordered to be returned by the construction unit. 2-5-3 Commercial concrete shall strictly follow the Code for Acceptance of Construction Quality of Concrete Structure Engineering (GB50204—2002) to examine the qualifications of suppliers of commercial concrete, examine and approve the mix proportion of commercial concrete, detect the slump at the pouring site, and keep test blocks for on-site witness test to ensure the construction quality of sand-gravel concrete. 2-5-4 Before the rail welding joint is formally welded, the construction unit is required to organize professionals to hold relevant certificates, debug the rail welding machine at the rail welding base, and conduct the rail welding test. After the flaw detector is qualified and the data is stable, the construction unit will organize a drop weight test, and then adjust the relevant parameters of the rail welder according to the test results. When the construction unit has passed the drop weight test for three consecutive batches, the supervision unit will participate in the test for three consecutive batches. If the test fails, the relevant parameters of the rail welding machine will continue to be adjusted and tested again. After all the tests are qualified, they will be sent to a third-party inspection unit for third-party inspection, and the welding can be formally carried out only after passing the inspection. After rail welding, the construction unit shall carry out rail flaw detection inspection. When the flaw detection wavelength exceeds the specified value, the construction unit shall be required to saw off the weld and re-weld. When the self-inspection 100% of the construction unit is qualified, the supervision unit will organize professional flaw detection personnel to conduct quality sampling inspection according to 10% of the total number of welding heads. Ensure the welding quality of rail welded joints and ensure the driving safety. See Table 3 for the testing units and testing items involved in the track project of Daxing Line. Conclusion For the quality control of track engineering materials, we should give full play to the initiative of the construction unit and manage different engineering materials separately according to the actual situation of the project. In the process of material inspection, the combination of appearance inspection and test inspection, the combination of self-inspection, supervision sampling inspection and parallel inspection by the construction unit, strict supervision procedures, strict laboratory qualification control, supervision, assistance and promotion can ensure the quality of track engineering materials and lay a foundation for effective control of track engineering quality.
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