Experimental investigation of initial deployment of inflatable structures for sealing of rail tunnels

Finite Element Simulation of Large-Scale Confined Inflatable Structures

“…Wong also adopted an inflator originally designed to simulate the inflation of automobile airbags [16][17][18]. The results reported by Wong, 2013 [14] matched reasonably well the experimental observations reported in [10,11,13] and provided a starting point that can be used as a reference for simulating similar inflatable structures installed in other tunnel configurations.…”

“…Experimental investigations of the initial deployment of large-scale structures showed that the initial shape achieved by the inflatable at the end of the initial deployment and inflation at low pressure is critical for maximizing the sealing capacity [13]. The presence of gaps in the contact between the inflatable and the inner tunnel surfaces not only reduces the frictional capacity to remain stable when subject to the external pressure but also increases the sources and amount of leakage that the inflatable is meant to contain [13].…”

“…From the operational point of view, experimental tests showed that the implementation of a large-scale inflatable for sealing one or more segments of a tunnel system could be divided into three main phases [9,13]: Phase 1, preparation and installation; Phase 2, initial deployment and inflation at low pressure; Phase 3, pressurization of the inflatable structure to contain the pressure of the threat, either gas or water. In Phase 1, the inflatable structure is folded and placed within a portable container that is then transported to a specific location of the tunnel segment and pre-installed.…”

“…Unlike the inflatable structures used in automobile and aerospace applications, which are relatively small and lightweight, the inflatables for protection of tunnels can have large dimensions and high weight due to the robustness needed in the fabric material to withstand the internal as well as the external pressures [13].…”

“…Experimental work carried out with full-scale prototypes demonstrated to be labor intensive and required multiple iterations to achieve consistent results. Moreover, experimental results reported in [11,13] indicated that the preparation procedures including the deflation, folding sequence and position of the deployment have an influence on how the membrane of the inflatable behaves during the initial deployment and then how it conforms to the tunnel section at the completion of inflation.…”