Abstract: Herein, a shield tail seal test platform modeling tail shield with an inner diameter of 2 000 mm is designed to  conduct a test on the sealing performance of shield tail under ultra-high water pressure up to 2 000 kPa. Shield tail sealing principles are analyzed, revealing the primary operations guaranteeing its performance, which is maintaining the maximum grease pressure higher than the external environmental mud and water pressure to ensure that the grease fully fills the tail seal gap and effectively resists the intrusion of external mud and water. Based on this instruction, targeted improvements are made to the tail seal system and pressure monitoring control system of the test platform. This platform adopts six tail brushes which can effectively transmit environmental pressure under high-pressure conditions while ensuring the safety of the tail brush steel plates. Additionally, 10 pressure monitoring points are arranged circumferentially in the grease chamber, enabling realtime monitoring and feedback of internal pressure changes. By establishing a pressure-increasing test scheme and using a pressure fluctuation within the grease chamber not exceeding 100 kPa as the evaluation criterion for sealing performance, a sealing test under 2 000 kPa water pressure is successfully completed, and the effectiveness of the test platform is verified. The experimental results show that by monitoring and adjusting the grease chamber pressure in real time and maintaining the maximum grease chamber pressure of 50 kPa higher than the external water pressure can achieve effective sealing performance of the tail seal system under the 2 000 kPa ultra-high water pressure environment. Furthermore, based on the analysis of experimental data and phenomena, a numerical calculation model is established, focusing on the influence of the number of grease injection ports and injection pressure on the grease chamber pressure. Multiple sets of empirical formulas are derived, which can be used to evaluate the time required for the grease chamber pressure to stabilize from the start of grease injection and the pressure drop of the stable pressure relative to the injection pressure.

Key words: high water pressure environment, shield, shield tail seal, quantity of grease chamber, pressure of grease chamber, numerical calculation