Evaluation Of Water-tightness Of Shield Tail Grease Under High Water Pressure And Its Influencing Factors Analysis

In recent years,the strait shield tunnel project has shown the trend of "high water pressure,long distance and large diameter",which poses more severe challenges to the engineering safety of shield tunnels.The great challenge to excavate the strait shield tunnel under high water pressure is unprecedented around the world.The increase of water pressure puts forward higher requirements on the sealing problem of the shield machine.As one part of the shield machine,shield tail sealing plays an important role in the engineering safety of shield tunnels.At present,the shield tail sealing mainly uses the method of filling the sealing grease between the multi-channel shield tail brushes,so the sealing performance of the grease directly affects the safety of the shield tunneling.Based on the practical issue,this study focuses on the water-tightness of shield tail sealing grease under high water pressure.The water-tightness test and computational fluid dynamic were conducted to study this problem.The major works are as follows:(1)Designed an equipment system to study the water-tightness of shield tail sealing grease under high water pressure,which can achieve stable water pressure within 0～4MPa range and simulate the dynamic effects of shield tunneling.(2)The above test device was used to carry out the water-tightness test for shield tail grease.According to the test results,the sealing performance of different greases was evaluated and the sealing method of grease was analyzed.In addition,the evaluation criteria for water-tightness of shield tail grease was proposed.(3)The water-tightness test and rheological test were conducted to study the influence of dynamic boundary and environmental factors such as temperature,water environment and sediment impurities on the water-tightness of the shield tail grease.(4)The computational fluid dynamic general software FLUENT were used to establish a numerical model of shield tail seal under high water pressure.Combined with the research results of the water-tightness test for shield tail grease,the sealing method and characteristics of shield tail grease are compared and analyzed.The effects of grease material viscosity and grease chamber length on the sealing performance of the shield tail were discussed too.