Abstract
A series of model tests were performed to investigate the load-bearing mechanism of a mined railway tunnel lining under water pressure. To investigate the load-bearing characteristics of different types of linings, a fully closed water pressure exerting device for a noncircular section tunnel was invented. A large-scale model test (1:30) under combined water and soil pressures was conducted to investigate the mechanical characteristics, deformation, stress distribution, crack development process, and failure mode of the underwater mined-tunnel lining. The test results indicated that for the high-speed railway tunnel of Class IV surrounding rock with a design speed of 350 km/h, both the drainage lining and the waterproof lining were controlled by a small eccentric compression under the two test conditions. One had only water pressure, and the other had a variable water pressure and constant soil pressure. The key sections for controlling instability were the bottom of the wall and the inverted arch. The ultimate water head of the drainage lining was 49 m, and the ultimate water head of the waterproof lining was 78 m. In comparison with the drainage lining, the waterproof lining could significantly improve the water-pressure resistance. Thus, design loads of 30 and 60 m are recommended for the drainage and waterproof lining structures, respectively.
Highlights
In Switzerland, Chabot studied the limited bearing water pressure of the waterproof lining, and the results indicated that the waterproof lining is relatively suitable for the water head range of 30–60 m
Literature reviews on the water pressure around tunnel structures have indicated that the research on tunnel seepage model tests is in the initial stage, and few studies have been performed in which the mechanism of the support system in the construction and operation stages was simulated with consideration of the water–soil coupling action [28,29,30,31,32,33,34,35]
According to the principle of mechanical equivalence, by using the “indirect” simulation method of hoop loading, a full-circle closed equivalent water pressure loading device was developed for the model test of a tunnel with a noncircular section, to achieve the nonuniform water loading of the mined-tunnel lining
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Literature reviews on the water pressure around tunnel structures have indicated that the research on tunnel seepage model tests is in the initial stage, and few studies have been performed in which the mechanism of the support system in the construction and operation stages was simulated with consideration of the water–soil coupling action [28,29,30,31,32,33,34,35]. The interaction between the surrounding rock and the support structures is complex, owing to the interaction between the stress and the seepage field This is a coupled process that is difficult to model and poses a threat to the lining structure, as the combined loading from water pressure and soil pressure can exceed the design capacity. Obtaining the limit indices for waterproof and drainage tunnels to withstand external water pressure can provide a basis for the safety design and construction-scheme selection of the underwater tunnel support structures, which has practical significance and considerable theoretical value
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