近距离桩基施工对既有盾构隧道的振动影响分析

Analysis on Vibration Influence of the Construction of Short-distance Pile Foundation on Existing Shield Tunnels

为分析预制桩打桩施工中冲击荷载作用下邻近既有盾构隧道的动力响应,依托成都轨道交通18号线倪家桥站—火车南站区间隧道工程,引入无限元静-动力统一人工边界,结合实际工程地质条件构建“桩-土-隧”三维动力有限元-无限元耦合模型进行数值试验,对比土工离心试验结果,验证了数值模型的有效性。基于此,研究了不同打桩参数对邻近既有隧道振动的影响规律,提出针对类似工程打桩施工引起的隧道峰值振动界限值。研究结果表明:(1)衬砌最大振动速度的分布位置反映振源与隧道的相对方位。隧道受打桩影响最不利的振动位置一般出现在隧道近桩侧1/4圆弧或者1/2圆弧上;(2)振动速度随打桩深度的增加而增大,当打桩深度超过隧道底部时,打桩深度增加对隧道振动的影响不再显著;(3)当在隧道上覆土柱范围内进行打桩施工时,桩隧水平间距对隧道振动的影响小于打桩深度的影响。

In order to analyze the dynamic response of the adjacent existing shield tunnel under the impact load during the construction of precast piles, relying on the tunnel project between the Nijiaqiao Station and the South Railway Station of Chengdu Rail Transit Line 18, the infinite element static-dynamic unified artificial boundary is introduced, and the "pile-soil-tunnel" 3D dynamic finite element-infinite element coupling model is constructed in combination with the actual engineering geological conditions for numerical tests. The results of geotechnical centrifuge tests are compared, and the validity of numerical model is verified. Based on this, the influence of different piling parameters on the vibration of adjacent existing tunnels is studied, and the limit value of tunnel peak vibration caused by piling construction of similar projects is proposed. The results show that:(1) The distribution of the maximum vibration velocity of the lining reflects the relative orientation of the vibration source and the tunnel. The most unfavorable vibration position of the tunnel affected by piling generally occurs on 1/4 arc or 1/2 arc near the pile side of the tunnel;(2) The vibration velocity increases with the increase of piling depth. When the pile driving depth exceeds the bottom of the tunnel, the influence of the increase of piling depth on the vibration of the tunnel is no longer significant;(3) When piling is carried out within the scope of the overlying soils pile above the tunnel, the influence of the horizontal spacing between piles and tunnels on the vibration of the tunnel is less than that of the piling depth.