不同直径匹配度封堵气囊的工作机理和试验验证

为研究气囊作为临时性封堵装置在隧道工程中的应用情况,建立其受力分析模型,得到了气囊内压和形状随外压增长的变化规律,得到了两种失效模式和正常工作时需要满足的3个控制条件,特别是外压不能大于内压这一独特的控制条件.由于气囊直径与隧道匹配度的大小直接影响封堵效果,因此确定直径允许误差范围在工程设计中至关重要.分别采用直径大于、等于、小于隧道直径的3种气囊进行堵气和堵水的模型试验,得到不同直径匹配度的气囊在气压和水压作用下的变形规律、内外压关系及失效极限状态的控制条件.试验结果表明:直径适中的气囊匹配性最好,气囊的变形和失效模式完全符合理论公式;直径略偏大的气囊若不出现初始贯通的褶皱,其封堵效果和失效模式与直径适中的气囊类似;直径偏小的气囊,由于一部分内压用于抵消使其膨胀至贴紧隧道壁所产生的材料拉力,容易导致其摩阻力不足而在外压作用下产生整体滑动.据此提出了气囊制作误差允许范围上下限的标准,为气囊制作过程中的误差控制提供依据.

Working mechanism and model test of plugging airbags with different diameter matching under external pressure

To study the application of airbags as a temporary plugging device in the tunnel engineering, the force analysis model was established to obtain the change law of the inner pressure and shape of the airbag as the external pressure increases. Two kinds of failure modes and three control conditions that need to be met during normal operation were obtained, in particular the unique control condition that the external pressure cannot be greater than the internal pressure. Since the matching degree between the airbag diameter and the tunnel directly affect the sealing effect, it is important to determine the allowable error range of the airbag diameter in the engineering design. Then the model tests were carried with three airbags with different matching degree. The deformation, internal and control conditions of the failure limit state were obtained. The results show that the airbag with the smallest deviation has the best sealability and the deformation and failure modes of the airbag are in good agreement with the theoretical formula. The airbag with a larger diameter has wrinkles, but the blocking effect and failure mode are similar to those with a moderate diameter. The smaller diameter of the airbag, due to a part of the internal pressure to offset the tension, has smaller maximum static friction resistance and it tends to slide under the external pressure. The allowable error of the airbag diameter is proposed, providing the basis for airbag manufacturing process.