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承载桩基对近距隧道具有明显的附加荷载作用,对于水敏性的大厚度湿陷黄土地层其影响更加明显。为系统研究桩基对近距隧道的影响,基于改进的离心浸水试验系统开展考虑不同桩端荷载、不同桩距比和不同地层浸水厚度影响下,承载桩基对近距隧道影响的离心模型试验。试验结果表明:(1)桩基附加荷载致使衬砌结构受力重分布,桩周土体对荷载传递具有削弱作用,桩端荷载越大,削弱作用越明显;土层浸水降低了其承载力,加剧了桩–隧间的荷载传递作用;随桩距比增大,桩基对隧道影响逐渐减小。(2)桩端荷载较小时隧道弯矩变化均匀,随荷载增加隧道向桩基方向发生扭曲,荷载进一步增加,隧道扭曲作用加剧;桩距比较小时,增大桩距比对弯矩变化影响减弱较明显,随桩距比增大,进一步增加桩距比对弯矩影响逐渐减小;土层浸水厚度较小时,受桩周土体的荷载削弱作用,桩基对隧道的影响较小,随浸水深度的增加,桩周土体承载力减弱,桩基对隧道的影响随之增加。(3)桩距比为1时,随桩端荷载的增加隧道最大下沉值达到16.7 mm,水平位移达到3.2 mm,随桩距比增加,隧道下沉和水平位移值均减小;随浸水厚度减小,隧道整体位移也减小,地基浸水导致的隧道位移主要表现为下沉,且浸水深度对隧道位移的影响弱于桩端荷载和桩距比。
The bearing pile has a significant additional load on the near tunnel, which has a more obvious effect on the water-sensitive large-thickness collapsible loess stratum. In order to systematically study the effect of pile foundation on the near tunnel, a centrifugal model test was conducted based on the improved centrifugal water immersion test system considering the effect of different pile end loads, different pile-to-pile ratios and different in-situ water thicknesses . The test results show that: (1) The additional load of the pile causes the stress distribution of the lining structure, and the soil around the pile has a weakening effect on the load transfer. The larger the pile load, the more obvious the weakening effect. The soil water loss reduces the bearing capacity, Aggravate the pile-tunnel load transfer role; as the pile spacing ratio increases, the pile foundation on the tunnel gradually reduced. (2) When the pile tip load is small, the bending moment of the tunnel changes uniformly. When the tunnel load increases, the tunnel distorts toward the pile foundation and the load increases further, and the tunnel twist is aggravated. When the pile spacing is small, the effect of increasing the pile-to-pile ratio on the bending moment is weakened Obviously, with the increase of the pile-to-pile ratio, the effect of further increasing the pile-to-pile ratio on the bending moment gradually decreases. When the thickness of the soaked soil is small, the load of the soil around the pile is weakened, and the pile foundation has less influence on the tunnel. With the increase of the water immersion depth, the bearing capacity of the soil around the pile is weakened and the influence of the pile foundation on the tunnel increases. (3) The maximum subsidence value of the tunnel reaches 16.7 mm and the horizontal displacement reaches 3.2 mm with the increase of pile-end load when the pile-to-pile ratio is 1. The subsidence and horizontal displacement of the tunnel decrease with the increase of pile-to-pile ratio. The thickness decreases and the overall displacement of the tunnel also decreases. The tunnel displacement caused by foundation immersion is mainly subsidence, and the influence of immersion depth on tunnel displacement is weaker than the pile-end load and pile-to-pile ratio.