Theoretical Analysis and Model Testing of the Deformation Characteristics and Failure Mechanism of a Blocking Airbag System in a Tunnel Under External Pressure

Abstract

With the development and utilization of underground spaces, subways and tunnels are often located in poor underground environments subject to problems with water and mud bursts. To reduce project losses, areas of gushing water must be isolated as soon as possible to enable repairs. To accomplish this isolation, the installation of a rubber airbag in a tunnel as a temporary retaining structure is proposed. An airbag is a membrane structure, which differs from a conventional structure. As a result, the force and deformation under the external pressure directly affect an airbag's slip failure mode. In this study, by combining the boundary conditions and stress conditions of an airbag in a tunnel, the rules governing the deformation of the airbag under uniform loading and the control conditions of the failure limit state are obtained. Model tests are conducted using airbags of two different diameters to block the external pressure, and the test results agree well with the theory. To improve the static friction resistance of the airbag and enable convenient and easy construction, a double airbag system is proposed. The deformation characteristics and failure mechanism of the double-airbag system are obtained from a force analysis. The double-airbag system blocks external pressure better and each of the airbags weighs less and easy to handling.