Determination of air pressure and assessment of air losses in clayey soil are of great importance to implementation of compressed air tunneling. In the present work, a series of air flow tests were performed to provide a more reasonable method based on flow characteristics of snap-off pressure and the dissolution/diffusion. Results showed that, the nonlinear air flow behavior and gas breakthrough were presented with the increase in air pressure. After that, the excessive pressure decreased continuously to reach an equilibrium termed as the snap-off. For the tested clayey soil, snap-off pressures around 250 kPa could be adopted as the air pressure, which was significantly lower than the gas breakthrough pressures. Diffusion coefficient of 1.5 × 10^-11 m²/s could be determined in the followed dissolution/diffusion stage, which bring 3 orders of decreasing magnitude in air losses compared to the capillary flow occurred after gas breakthrough. As a conclusion, the adoption of snap-off pressure in compressed air tunneling could effectively prevent the continuous air/water flow in clayey soil and create a more human-friendly environment. Additionally, less air losses could be presented compared to that using gas breakthrough pressure, indicating tremendous energy savings in field implementation.

确定粘土中的空气压力和评估空气损失对实施压缩空气隧穿非常重要。在目前的工作中，进行了一系列气流测试，以基于折断压力和溶解/扩散的流动特性提供一种更合理的方法。结果表明，随着空气压力的增加，空气的非线性流动行为和气体突破表现出来。在那之后，过大的压力连续下降以达到所谓的折断（snap-off）平衡。对于测试的黏性土，可以采用250 kPa左右的折断压力作为空气压力，该压力明显低于气体的突破压力。扩散系数1.5×10 ^-11 m ²/ s可以在随后的溶解/扩散阶段确定，与气体突破后发生的毛细流动相比，空气损失减少了3个数量级。结论是，在压缩空气隧道中采用折断压力可以有效防止黏性土壤中连续的空气/水流动，并创造更人性化的环境。另外，与使用气体突破压力相比，可以减少空气损失，这表明在现场实施中可节省大量能源。