At 21:58 on September 22, the right line shield tunnel between Xingcun Station of Jinan Rail Transit Line 8 and Youth Political College Station (hereinafter referred to as the project name) was successfully completed, marking the opening of the first phase of the project of Line 8 and one step closer to the goal of completion and opening to traffic by the end of 2025.
The first phase of the project of Line 8 starts from Xingcun Station in the west to Qingyuan Street Station in the east, with a total length of 25.5 kilometers, of which the underground section is about 5.6 kilometers. Since the launch of the first TBM on December 8, 2023, it has only taken 289 days for the underground section to be fully completed, 83 days ahead of schedule.
The shield construction of the first phase of Line 8 has the characteristics of "three difficulties and one fast": the construction organization of "one station and four starts" of shield tunneling is difficult, the geological complex and changeable tunneling process is difficult, and the safety control of crossing multiple risk sources is difficult, but the builders continue to overcome difficulties, the construction speed is fast, and the tunneling record is continuously refreshed.
Difficult construction organization: shield "one station and four shots"
Restricted by objective factors, 4 of the 5 shield machines of Line 8 started at the Youth Political College Station, and the prefabrication and assembly of the station and the shield tunneling construction were carried out simultaneously, and the cross construction was serious; Eight "small trains" with a length of about 64 meters to transport muck and segments shuttle through the 230-meter station, which is very easy to cause "traffic jams" and bring great challenges to the construction organization.
In response to these problems, the construction project department of Line 8 organized the construction unit CCCC No. 2 Public Bureau to scientifically plan the construction process, reasonably divide the construction area, strengthen the dynamic control of cross construction, and arrange special personnel to monitor and control each area to minimize the risk of cross construction and ensure the orderly progress of various processes.
The tunneling process is difficult: the geology is complex and changeable
The underground section of Line 8 has uneven geology, complex and changeable, including moderately weathered marl, moderately weathered limestone, strongly weathered marl, gravel, loess, silty clay, silt and other geologies, and there are karst caves. The shield machine crosses the "soft and hard" strata for a long distance, which is easy to cause abnormal wear of the cutter and affect the construction efficiency.
According to the actual situation, the personnel of the project department optimized the selection of the shield machine and the configuration of the tools, and regularly opened the warehouse to check the wear of the tools in accordance with the principle of "frequent inspection and change, fast in and fast out", which greatly reduced the risk of unplanned downtime. For karst formations, they carried out infill supplementary survey on the basis of detailed survey, strengthened the fine control of complex geology, and adjusted the tunneling parameters and grouting parameters in a timely manner to ensure the safe and efficient excavation of the shield machine.
Difficult to manage and control security: Crossing multiple risk sources
The underground section of Line 8 is basically located below Jingshi East Road, which has high requirements for ground settlement and deformation. The Xingqing section shield tunnel spans the tunnel between Line 4 and passes through many risk sources such as Liugong River, Tuhe, China Railway City pedestrian bridge, Gangxi interchange ramp bridge, etc., which has high requirements for tunneling parameter control and shield machine attitude. In particular, the shield tunnel spans the Line 4 tunnel, with a vertical clear distance of only 2.87 meters, and the Line 4 tunnel has completed the construction of track laying, strong and weak electricity, evacuation platform and other facilities in the tunnel.
In order to ensure the absolute safety of the construction process, the project department of Line 8 carefully formulated a special construction plan, organized experts to repeatedly demonstrate, determined the main construction risks and control points, set the test section before the crossing to clarify the reasonable tunneling parameters, and implemented 24-hour uninterrupted ground and tunnel monitoring and inspection during the crossing period, laying a solid foundation for construction safety.
The construction speed is fast: the average monthly excavation is 230 meters
The construction of the Youth Political College Station adopts the green construction technology of prefabricated and superimposed structures, and the construction of the main structure of the station and the construction of the shield can be carried out simultaneously, which is 2 months earlier than the start of the shield construction technology of the traditional station. In order to speed up the efficiency of shield tunneling, the project department of Line 8 paid close attention to project management, formulated construction plans in detail, strengthened the assessment and evaluation of engineering nodes, implemented efficient green disposal technology for shield muck, and solved the problem of shield tunneling shutdown caused by the obstruction of muck transportation through muck screening and filter pressing.
In addition, the construction unit CCCC No. 2 Public Bureau through the continuous optimization of resource allocation and construction procedures, the selection of professional ability, rich construction experience of management personnel and labor teams, set up super ring progress awards, winning team awards, outstanding staff awards and other selection activities, monthly safety, quality, progress, civilized construction and other assessment and evaluation, effectively mobilized the enthusiasm of personnel, the highest single-day excavation of 36 meters, the average monthly excavation of 230 meters, and constantly refresh the shield excavation record in the weathered limestone formation.
(Source: Jinan Rail Transit)