Recently, with the rapid advancement of China's rail transit construction, shield tunneling technology has become the core method for underground tunnel construction in urban rail transit due to its characteristics of minimal environmental interference, high construction efficiency, and strong adaptability. The shield tunneling construction of rail transit is a complex project that integrates mechanical, electrical, hydraulic, geological and other disciplines. During the construction process, it is affected by various factors such as geological conditions, underground pipelines, and ground structures. The scientific and accurate technical control directly affects construction safety, engineering quality, and tunnel service life.
The technical control of shield tunneling construction in rail transit follows the core principles of "pre preparation, in-process control, and post closure", which runs through the entire process of shield tunneling initiation, excavation, pipe assembly, wall grouting, and shield tunneling reception. The technical control of each link is crucial, and it needs to be combined with engineering geological conditions and construction reality, accurately implemented and scientifically controlled to ensure that the construction process is orderly and controllable, and to guarantee the quality and safety of tunnel construction. Industry experts say that the core of shield tunneling construction technology control is "precise control and dynamic adjustment", which needs to balance construction efficiency and engineering quality, and timely respond to various geological and technical problems that arise during construction.
The technical control of the shield tunneling starting stage is the foundation of the entire construction process, which directly affects the smooth progress of subsequent construction. The main control points include starting preparation, shield tunneling positioning, and hole reinforcement. Before construction, a detailed geological survey must be completed, and a special construction plan must be developed based on the survey report to clarify the shield tunneling process, technical parameters, and emergency measures. After approval, it can be put into implementation. At the same time, a comprehensive inspection and debugging of the shield machine is required, with a focus on the tool system, hydraulic system, electrical system, and auxiliary equipment to ensure that the wear of the rolling cutter meets the requirements, the hydraulic system is leak free, and the electrical equipment is operating normally. All inspection records must be signed and confirmed by the technical supervisor.
The positioning of the shield machine requires precise control, and the axis, elevation, and posture of the shield machine are calibrated through professional measuring equipment to ensure that the starting direction of the shield machine is consistent with the design axis and avoid deviation. The reinforcement of the strata at the entrance of the tunnel is a key safety control point during the starting stage. Usually, grouting, freezing and other methods are used for reinforcement to prevent hidden dangers such as tunnel collapse and water seepage during the shield tunneling of Chongqing Metro Line 15. During the shield tunneling construction of the tunnel, the project team optimized the reinforcement plan based on the geological characteristics of the entrance area, providing a guarantee for the smooth starting of the shield tunneling. In addition, a reaction frame needs to be installed before departure to ensure its strength and stability, providing sufficient propulsion reaction force for the shield machine. At the same time, the rubber sealing strip at the entrance of the tunnel should be checked and water stop measures should be taken.
The technical control of shield tunneling stage is the core link, which directly determines the quality and progress of tunnel construction, mainly covering key points such as excavation parameter control, attitude control, and slag management. The excavation parameters need to be dynamically adjusted according to geological conditions, with core parameters such as excavation speed, thrust, cutterhead speed, and grouting pressure pre-set in advance. For soft rock formations, the excavation speed can be appropriately increased, while for hard rock formations, the speed needs to be reduced and the thrust increased. Generally, the excavation speed is controlled at 0.5-1.2 meters per minute, the cutterhead speed is controlled at 2-5 revolutions per minute, and the grouting pressure is controlled at 0.2-0.4 megapascals. After inputting the parameters, the accuracy needs to be tested and verified in simulation mode.
During the excavation process, operators need to record key data every 5 minutes and monitor the posture of the shield machine in real time, including pitch angle, horizontal deviation angle, etc. If the axis deviation exceeds the specification requirements, the correction system should be activated in a timely manner to avoid excessive deviation of the tunnel axis, which will affect the subsequent assembly of pipe segments and tunnel use. At the same time, it is necessary to closely observe the state of the excavated soil. Abnormal increase in soil moisture may indicate groundwater infiltration, and timely measures to stop water should be taken; When the temperature of the cutterhead exceeds 80 ℃, it is necessary to suspend construction and check the cooling system to prevent tool damage. 97% of the mileage of the Dazhang section of Chongqing Rail Transit Line 15 is sandstone and sandy mudstone. The project team dynamically adjusted the excavation parameters, selected reinforced rolling cutters and efficient disc washing devices, effectively avoiding disc "mud cake formation" and ensuring smooth excavation.
The control of pipe segment assembly technology is the key to ensuring the quality of tunnel lining. As the innermost barrier of the tunnel, the assembly quality of pipe segments directly affects the waterproof performance and durability of the tunnel. Before assembling the pipe segments, it is necessary to conduct a strict inspection of the quality of the pipe segments, check the type and number of the pipe segments, inspect the surface damage and the adhesion of the water stop sealing strip. Unqualified pipe segments shall not be used. When assembling, the sequence of "starting from the lower standard block, installing alternately left and right, and finally installing the top block" should be followed. The staggered assembly method should be used to ensure that the assembly surface is flat, and the gap between the pipe segments should be controlled at 3-5 millimeters. During the assembly process, the shield jacks should be retracted and topped up according to the assembly sequence to prevent the shield from retreating and the excavation surface from becoming unstable.
After the assembly of the pipe segments, it is necessary to use a torque wrench to tighten the connecting bolts as required. First, tighten the circumferential bolts, then tighten the axial bolts. After pushing to a position where the jack thrust does not affect it, tighten the bolts again to avoid loosening and affecting the stability of the lining. At the same time, it is necessary to clean the tail area of the shield in a timely manner to prevent residual soil from affecting the quality of assembly. After assembly, check the misalignment and cracks of the pipe segments. The misalignment of adjacent pipe segments should not exceed 10 millimeters, and the maximum crack width should not exceed 0.2 millimeters. Unqualified parts should be repaired in a timely manner.
The control of grouting technology behind the wall is an important means to prevent tunnel settlement and improve tunnel waterproofing performance. It should be carried out in a timely manner after the assembly of the pipe segments, following the principle of "synchronous grouting and timely grouting". The grouting material needs to be tested and selected with high strength, good fluidity, and suitable solidification time. Commonly used materials include cement slurry, cement mortar, etc. Before construction, the viscosity and solidification time of the slurry need to be tested to ensure compliance with design requirements. The grouting pressure and grouting volume need to be accurately controlled, adjusted according to the depth of the tunnel and geological conditions, to avoid excessive pressure causing damage to the pipe segments, or insufficient pressure affecting the grouting effect. After grouting is completed, the grouting density should be checked, and the unconsolidated areas should be treated with grouting to prevent later settlement caused by voids.
The technical control of the shield receiving stage is equally important as the starting stage, with the core being to ensure the safe and smooth passage of the shield machine out of the tunnel. The main control points include reinforcement of the receiving end, adjustment of the shield posture, and sealing of the tunnel opening. Before receiving, it is necessary to reinforce the ground layer at the receiving end, clean up obstacles at the entrance, check the sealing device at the entrance, and prepare for waterproofing; When the shield machine approaches the receiving hole, it is necessary to slow down the excavation speed, adjust the posture accurately, ensure that the shield machine smoothly passes through the hole, and avoid colliding with the hole structure. After receiving, promptly seal the entrance of the tunnel to prevent groundwater infiltration, and conduct comprehensive maintenance of the shield machine to prepare for subsequent construction or equipment transportation. In addition, during the receiving phase, it is necessary to strengthen on-site monitoring, pay real-time attention to ground subsidence and structural deformation around the entrance, and promptly handle various emergencies to ensure a safe construction loop.
The reporter learned that the technical control of shield tunneling construction in rail transit still needs to pay attention to the whole process monitoring. Before construction, a complete monitoring system should be established, and monitoring points such as ground settlement, tunnel axis, and pipe stress should be set up. Real time monitoring data should be collected during the construction process. If there are any abnormalities in the data, the reasons should be analyzed in a timely manner and construction parameters should be adjusted to prevent safety hazards. At the same time, the construction unit needs to strengthen the professional training of construction personnel, enhance their mastery of shield tunneling equipment, construction technology, and emergency response capabilities, standardize operating procedures, and ensure the effective implementation of technical control measures.
Industry experts have stated that as rail transit construction deepens and becomes more complex, the difficulty of controlling shield tunneling construction technology continues to increase. The application of new intelligent monitoring equipment and shield tunneling machine upgrade technology provides strong support for precise control. In the future, we will further promote the refinement and intelligence of shield tunneling construction technology, optimize technical control processes, improve emergency response plans, provide guarantees for high-quality construction of rail transit projects, and help create a safe, efficient, and durable urban rail transit network.
Copyright © 2026-2043 Guizhou Yichenzi Construction Engineering Co., Ltd
