盾构隧道管片壁后注浆厚度对隧道抗浮影响研究

Study on Effect of Backfilling Grouting Thickness on Anti-floating of the Shield Tunnel

在富水粉砂土地层中,地震液化作用易引起盾构隧道管片上浮,进而导致隧道结构破坏。文章通过振动台模型试验与数值模拟相结合的方式,研究了盾构隧道采取壁后注浆措施前后周边液化地层的动力响应,揭示了盾构隧道的主要破坏模式为液化上浮。在峰值加速度保持不变的情况下,采取壁后注浆的方式虽然不能明显缓解地基土的液化趋势,但可以显著降低模型隧道的上浮位移量。数值模拟结果与试验结果表明:砂土液化最先发生在地表及浅层土体处,随着模型深度的增加,砂土的液化程度逐渐降低,即增加隧道埋深有利于降低隧道液化程度。壁后注浆体通过与隧道结构形成整体,间接增大了上覆有效压力,能够抵消地基液化产生的上浮力。对于直径为6.2 m的盾构隧道,通过管片二次注浆孔进行注浆加固,浆液渗透半径达到1.0 m以上将能产生非常明显的抗液化上浮效果。

Sand liquefaction will occur and result in tunnel uplift and even damage under the effect of earthquake when the shield tunnel passes through sandy soil stratum.The dynamic response of the surrounding liquefied strata before and after backfill grouting of the shield tunnel is studied by shaking table model test and numerical simulation,and it shows the main damage pattern of the shield tunnel is liquefaction induced uplift.Backfill grouting can’t significantly alleviate the liquefaction tendency of subsoil,but the uplifting displacement of the tunnel model can be remarkably reduced if peak acceleration keeps unchanged.The numerical simulation and test results show that the sand liquefaction firstly occurs at the surface and shallow soil layer,and the sand liquefaction degree gradually decreases with the increase of depth,that is to say increase of tunnel buried depth is conducive to reducing liquefaction degree.Integrity is formed by backfilling grouts and tunnel structure and this increases the overlying effective pressure indirectly and can offset the uplift induced by foundation liquefaction.For the shield tunnel with a diameter larger than 6.2 m,obvious anti-uplift effect will be obtained if the grout penetration radius is larger than 1.0 m in condition of grouting reinforcement.