考虑空洞影响的盾构隧道地震易损性分析

Seismic vulnerability analysis of shield tunnels considering cavitation

管片背后存在空洞是盾构隧道一种常见的病害现象,它不仅影响土层和管片的静力学行为,还会影响隧道的动力响应,加剧隧道地震破坏。现有的相关研究均采用确定性分析方法,缺少从概率角度的定量评价。以某轨道交通区间盾构隧道为例,考虑空洞位置和尺寸、场地条件以及地震波入射方向等因素,采用动力增量法,开展了基于土层-隧道-空洞相互作用的大量非线性动力时程分析。结合隧道地震易损性理论,研究存在空洞病害的盾构隧道地震易损性。结果表明:空洞尺寸、场地条件和地震动入射方向对隧道地震易损性有重要影响。随着空洞尺寸的增加,空洞及临近区域土体塑性变形成倍增大,管片截面偏心程度增加,承载性能减弱,受影响范围为空洞尺寸的3~5倍。管片背后空洞增大了隧道结构的易损性,空洞越大,易损性增幅越明显。空洞对结构易损性的影响因空洞部位不同而异,在较大尺寸空洞时,影响程度由大到小依次为:边墙、拱肩和拱顶空洞。场地条件越差,会增大隧道的易损性,空洞对易损性的影响也越大。横向和垂向地震动入射方向下,隧道易损性均随空洞尺寸的增加呈非线性增大,虽然垂向地震动下的损伤概率小于横向地震动,但增幅明显更大,受空洞尺寸的影响更为敏感。值得注意的是,针对3种空洞部位和两种地震动入射方向,较大的空洞尺寸都将显著影响结构的抗震性能。

The existence of cavities behind the segments is one of the common disease phenomena in shield tunnels.The cavities not only affect the static mechanics behavior of soil and segment,but also directly affect the dynamic response of the tunnel,which could aggravate the tunnel’s seismic damage.The existing related researches all use the deterministic analysis methods and lack the quantitative evaluation method in terms of probability perspective.Taking a shield tunnel in a rail transit section as an example,considering factors such as the location and size of the cavity,site conditions,and the incident direction of seismic wave,a large number of nonlinear dynamic time-history analyses are conducted based on the soil-tunnel-void interaction using an increment dynamic analysis method.Combined with the theory of tunnel seismic vulnerability,the seismic vulnerability is studied for the shield tunnel with the cavity disease.It is found that:the size of the cavity,the site conditions and the incidence direction of seismic wave have an important influence on the tunnel seismic vulnerability.As the cavity size increases,the plastic deformation of the soil adjacent to the cavity increases substantially,the eccentricity extent of the segment section increases,and the load-bearing performance decreases,and the affected area is about 3-5 times the cavity size.The cavity behind the segment increases the vulnerability of the tunnel structure.The increase of vulnerability is more obvious with the void size increasing.The impact of the cavity on the structure vulnerability varies with different locations of the cavity.When the cavity size is relatively large,the impact extent shows the following trend with a descending order:the side wall,shoulder,and crown cavity.As site condition worsens,the tunnel vulnerability increases and the influence of the void on tunnel vulnerability also enhance.Under the transverse and vertical incident directions of seismic ground motions,the tunnel vulnerability increases nonlinearly with the increasing of the cavity size.Although the damage probability under vertical ground motion is less than that of transverse ground motion,the increasing extent is significantly larger and more sensitive to the cavity size.It is worth to noting that for the three cavity locations and the two incident directions of ground motion,the larger cavity size may significantly affect the seismic performance of the tunnel structure.