Experimental Study of Sealing Performance Test Methods and Sealing Mechanism of Shield Tail Sealing Grease

Throughout this research, five different types of sealing grease samples were collected from the construction sites of shield tunnels and tested with the current sealing test methods. For the purpose of assessing the sealing performance more accurately, a new test method was proposed based on the test results. Through this test method, the maximum diameter of pores (MDPs) that can be blocked by sealing grease was considered as the indicator of sealing performance. Furthermore, it was found that sealing grease basically seals the micropores by forming a sealing layer. If the sizes of the micropores exceeded the MDP, the sealing grease was observed to be leaking until the seal barrier was penetrated by pressure. The MDP is not affected by pressure or time. Through the microscopic images, it was observed that the thickness of the sealing layer increased with the sizes of the micropores. The new test method was used to test the samples of prepared sealing grease with varied fiber contents and it was found that sealing performance improved with increase in fiber content while simultaneously filtration decreased.