Recently, at a scientific and technological achievement evaluation meeting organized by China Railway Construction Corporation (CRCC), the scientific and technological achievement "Shield Tail Sealing Grease Testing Technology for Shield Tunneling Machines" independently developed by China Railway 14th Bureau Group was recognized by the expert panel as reaching the "international leading level." In addition, the supporting equipment for this technology, the "Water Flow Scour Loss Resistance Test Device for Shield Tail Sealing Grease of Shield Tunneling Machines," was also rated as a first prize winner of the 2023 CRCC Young Employees' "Five Small" Innovation Achievements.

Internationally Leading Technology

In recent years, shields, as a mainstream construction method, have demonstrated strong advantages in urban underground construction. With the continuous development and maturation of domestic shield construction technology, there has been an increasing number of tunnel projects featuring long distances, large diameters, great burial depths, high water pressure, and complex cross-sections.

During construction, to ensure the safe tunneling of the shield machine, the reliability of the tail seal must be improved as much as possible, and shield tail sealing grease is an important functional material for ensuring tail seal performance. During shield tunneling, shield tail sealing grease at a certain pressure must be injected to fill the gaps in the tail brushes, forming a pressure seal chamber that prevents the infiltration of groundwater and slurry. Once the quality of the shield tail sealing grease is poor, or the amount or pressure is insufficient, it can easily lead to poor or even failed tail sealing performance.

China Railway 14th Bureau Group found that there is currently no unified testing technology or standard specification for shield tail sealing grease on the market, and the quality of grease products on the market varies greatly, affecting the healthy development of the shield industry.

Group Standard for Shield Tail Sealing Grease of Shield Tunneling Machines

To this end, China Railway 14th Bureau Group set out to develop shield tail sealing grease testing technology for shield tunneling machines, organizing project initiation, conducting subject experiments, and completing project acceptance and achievement appraisal, all independently. Through this technology, China Railway 14th Bureau Group unified the performance testing equipment and test methods for shield tail sealing grease, compiled the group standard Group Standard for Shield Tail Sealing Grease of Shield Tunneling Machines, provided product optimization standards for shield tail sealing grease manufacturers, enhanced the overall level and market competitiveness of domestic products, and also provided construction units with a basis for selecting shield tail sealing grease based on performance quality.

First Prize for "Five Small" Achievements

Award Document for the Company's "Five Small" Innovation Achievements

To meet the current demand for green, low-carbon, and environmentally friendly building engineering materials and to better implement the national ecological civilization construction and "dual carbon" policies, the "Geng Jingwei Female Employee Innovation Team" also newly added environmental protection, safety, and other indicators to the standard, and successfully developed supporting equipment, the "Shield Tail Grease Water Flow Scour Loss Resistance Test Device."

Description of the Water Flow Scour Loss Resistance Device in the Group Standard Group Standard for Shield Tail Sealing Grease of Shield Tunneling Machines Published and Issued by Standards Press of China

During the improvement of the test equipment, targeting the adhesive properties of grease, the research team developed a high-pressure water supply device and a spray device, achieving the technological innovation of "using water flow scour loss instead of water spray"; targeting the water-insoluble property of grease, the equipment achieves water-oil separation by installing separate storage tanks and collection tanks, avoiding the discharge of oily wastewater and reducing grease pollution to the external environment. Test personnel can also use the mixed liquid in the collection tank to further carry out research related to biological toxicity tests.

Members of the Geng Jingwei Female Employee Scientific and Technological Innovation Team Discussing the Testing Process

During the improvement of the test methods, the research team found that excessive water content in the grease was the main cause of large deviations in test results. After repeated attempts, the team set up a series of temperature controls and ultimately overcame this problem, enabling the overall testing process to be realized. In addition, targeting the problem that grease is viscous and difficult to shape, the research team innovatively adopted a test method that indirectly controls specimen thickness by controlling template thickness, making the specimen preparation process more consistent with the characteristics of grease and the steps more scientific and standardized.

At present, the related supporting testing technology has been promoted and applied, and testing commissions have been undertaken from multiple grease manufacturers and shield construction units, successfully achieving commercialization of the results and empowering the high-quality development of the enterprise.

Members of the Geng Jingwei Female Employee Scientific and Technological Innovation Team

In recent years, China Railway 14th Bureau Group has given full play to employees' innovation and efficiency-creating capabilities, extensively carrying out mass economic and technological innovation activities mainly based on young employees' "Five Small" innovation, model worker innovation studios, and innovation alliance construction, promoting the implementation and commercialization of a series of innovative achievements characterized by "solving on-site construction problems, improving frontline production efficiency, driving project benefit improvement, and promoting construction safety production."