超大直径盾构隧道横通道离心模型试验研究

Centrifuge Model Test of the Cross Passages in Super Large Diameter Shield Tunnels

为了探究超大直径盾构隧道开设横通道时,不同埋深、不同开口型式对主体结构受力及变形的影响,依托北京东六环改造项目盾构段人行横通道工程,通过离心模型试验模拟三种埋深条件下不同开口尺寸与断面型式的工况,对盾构段隧道结构开口环应力状态、收敛变形、管片环间错台及隧道周围土压力进行监测。研究结果表明:(1)当离心加速度达到设定值时,土压力趋于稳定,埋深越大达到稳定所需的时间越长;隧道上覆土体存在一定的土拱效应,埋深越大其土拱效应越加明显;(2)盾构隧道侧向开口对主体结构受力具有显著影响,开口尺寸越大,结构的变形越大;(3)在不同埋深工况下,管片环间错台量随离心加速度的增大而增大,且增大速率逐渐提高;(4)不同埋深工况下,主体隧道拱腰内侧应力状态基本相同,均为压应力;拱腰外侧应力的规律较为复杂,开口环的压应力集中将抵消一部分拉应力,除开口环外的其他相邻环的拱腰处外侧主要承受拉应力。

In order to explore the influence of different buried depths and opening types on the stress and deformation of the main structure when a cross passage is set up between super large diameter shield tunnels, based on the project case of the pedestrian cross passage of the shield section tunnel in Beijing East Sixth Ring Road Reconstruction Project, the stress state, convergence deformation, dislocation between segments and rings and earth pressure around the tunnel opening ring of the shield section tunnel structure are monitored by centrifugal model test to simulate three cases of buried depth, different opening sizes and section types. The results show that:(1) When the centrifugal acceleration reaches the set value, the earth pressure tends to be stable, and the greater the buried depth is,the longer the stabilization time will be required. The soil arching effect exists in the overlying soil of the tunnel, and the greater the buried depth is, the more obvious the soil arching effect will be.(2) The lateral opening of the shield tunnel has a significant impact on the stress of the main structure. The larger the opening size is, the greater the deformation of the structure will be.(3) Under different buried depth cases, the dislocation between segments increases with the increase of centrifugal acceleration, and the increase rate gradually rises.(4) Under different buried depth cases, the stress state on the inside of the main tunnel arch waist is basically the identical, which is compressive stress. The pattern of the stress at the outside of the arch waist is more complex. The compressive stress concentration of the split ring will offset a part of the tensile stress, and the outside of the arch waist of other adjacent rings except the split ring will mainly bear the tensile stress.