Mechanical Properties of Evacuated Tube Transport Double Lining Structure

In order to ensure the sealing performance of the evacuated tube transport (ETT) system, a structure combining shield segment and secondary lining was proposed. Based on the numerical simulation model of double-layer lining, taking Shanghai silt clay as the simulated stratum, the internal force distribution of ETT of composite double-layer lining structure and superimposed lining structure is simulated and analyzed respectively. Compared with the internal force of conventional shield tunnel, the ETT internal force distribution difference between composite double-layer lining and superimposed lining structures is analyzed; mechanical properties such as differential pressure load increment caused by axial force and contact pressure between the layers are discussed; the effects of differential pressure load, vertical load, and structural forms on the internal forces of the double-layer lining structure are studied. The results show that the pressure differential load has no effect on the bending moment of the double-layer lined ETT, but it will cause the increment of axial force. When the vertical load is small, the pressure differential load will cause the disconnection zone of the double-layer lining structure of ETT, and the disconnection zone will develop gradually with the decrease of the vertical load. The bending moment value of the segment and second lining of the composite double-layer lining structure ETT is generally larger than that of the superimposed lining structure. Under larger load conditions, the uneven distribution of axial force in the composite cross-section is more prominent than that in the superimposed cross-section.