Gas sealing behavior of gasketed segmental joints in shield tunnels: An experimental and computational study

Abstract

When shield tunnels pass through gas-bearing strata, gas leakage through could damage tunnel structure and interior equipment during both construction and operation process. Previous studies on sealing behavior of the gasketed joints have focused on the waterproof performance. However, differences in physical characteristics between liquid and gas lead to different permeation properties. This paper presents a combined experimental and computational study to investigate the gas sealing behavior of the gasketed joints in a shield power tunnel project, named as Sutong GIL Utility Tunnel, which passes through soft soil strata rich in high-pressure biogas under Yangtze River. The tests are aimed to measure the air leakage rates through the gasketed joints with various combinations of joint openings and offsets under different pressures. Slight leakage and rapid leakage are defined in the tests, where the leakage rates differ drastically in magnitude. This paper takes critical pressure, which corresponds to the leakage rate of 100 ml∙min−1 per meter joint length, as the index of the capability to resist sealing failure under extreme conditions, takes leakage rate as the index of gas sealing performance during long-term ‘slight leakage’, and evaluates the effects of the joint deformation on the gas sealing behavior from the two aspects. Finite element models of the inner gasket-groove structure were created and set with different joint openings and offsets, loaded with different pressures. Gasket deformation and contact stress under different conditions were studied. Comparison between the numerical results and test results was made to investigate the gas sealing behavior. Based on the existing gas sealing model of rough surfaces, a computational method of leakage rate was developed and validated, which can be used at the stage of long-term ‘slight leakage’. Based on the study, gas sealing behavior of the gasketed joints was analyzed and suggestions of improvement were given.