Deflation analysis of an air cushion for underwater shaking tables

The deflation process of inflatable membrane structures has always been a topic worthy of in-depth research. Inflatable membrane structures are employed for waterproofing in underwater environments, and their deflation process often poses safety concerns, warranting increased attention. An air cushion, which is applied to waterproof the underwater shaking table, is researched. It is arranged between the shaking table and the cover plates and can provide waterproof protection for the driving equipment of the shaking table. This article mainly studies the complete process of deflation for the waterproof air cushion. Force analysis was conducted on the air cushion membrane at different stages of deflation, and the factors that affect force during the deflation process were determined. A simulation method that combines the CEL (Coupled Eulerian-Lagrangian) method and fluid cavity method was used to analyze the deflation process of the air cushion, taking into account the effects of different deflation speeds and initial inflation pressures on the process. Based on the analysis results of the pressure-air volume curve and the deformation of the air cushion, the deflation process can be divided into three stages: elastic shrinkage stage, extrusion deformation stage, and free deformation stage. Based on the analysis results of dynamic stability, the extrusion deformation stage is further divided into two sub-stages: the extrusion stable stage and the extrusion unstable stage. It was found that the air cushion can achieve stability during both the elastic shrinkage stage and the extrusion stable stage, leading to the proposal of an evaluation method for air cushion deflation. Finally, the instantaneous leakage process of different positions on the air cushion was analyzed, and engineering suggestions were provided based on the analysis results. The research results provide a reference for the application of underwater inflatable membrane structures.