渗流作用下粉砂地层中盾构隧道开挖面失稳模式离心试验研究

Centrifugal test study on instability mode of shield tunnel excavation facein silty sand stratum under seepage

为研究渗流情况下开挖面支护力变化规律及失稳破坏模式,开发一整套离心模型渗流试验装置。通过开展不同内摩擦角干土和不同水头压力饱和土的试验,研究了不同土质开挖面支护力变化规律和前方土体渐进破坏机理,分析了同一种土渗流力对开挖面支护力及失稳响应机制的影响。结果显示,随着开挖面后撤位移S的增大,开挖面支护力P分为迅速下降(S<1.5D%)、到达极限支护力Plim后缓慢回弹(1.5D%≤S≤3D%)、逐渐趋于稳定值(3D%<S)3个阶段;开挖面支护力随着内摩擦角的增大而较小,随着水头压力的增大呈线性增大;土体失稳模式与土体内摩擦角有关,是一个由局部破坏到整体破坏的渐进过程,不同内摩擦角土体在土拱迭代过程中响应时间不同,渗流力加剧了土拱迭代速度和破坏力度,验证了渗流力具有各向异性。

In order to study the law of support force change and failure mode of excavation face under seepage,a set of centrifugal model seepage test device was developed.Based on the tests of dry soil with different internal friction angle and saturated soil with different head pressure,the change rule of support force and progressive failure mechanism of soil in front of excavation face of different soil are studied,and the influence of the same soil seepage force on support force and instability response mechanism of excavation face is analyzed.The results show that with the increase of the displacement S,the supporting force P is divided into three stages:the rapid decline(S<1.5 D%),the slow rebound after reaching the ultimate supporting force Plim(1.5 D%≤S≤3 D%)and the steady value(3 D%<S).The support force of excavation face is smaller with the increase of internal friction angle,and increases linearly with the increase of head pressure;The instability mode of soil mass is a gradual process from local failure to global failure related to the internal friction angle of soil mass,soils with different internal friction angles have different response times during iteration of soil arch and seepage force exacerbates soil arch iteration speed and destruction.Finally,it is verified that the seepage force is anisotropic.