海底盾构隧道全寿命抗震性能研究

The plan and construction of tunnels connecting all major coastal economic zones in China are striding forward, and the construction of world-class subsea tunnels including Qiongzhou channel tunnel, Bohai channel tunnel will come up in near future. The coast of our country lies in the circum-Pacific seismic belt, which is one of the two major seismic zones in the world. Especially, Bohai channel, Taiwan channel, and Qiongzhou channel are in the active area with strong earthquake where seismic activities happened frequently in recent years. Consequently, the seismic safety of tunnel projects should be paid more attention. Combined with the ground motion characteristics of offshore engineering site, properties of offshore marine geological body, marine erosion environment and shield tunnels, aimed at the life-cycle seismic performance of subsea shield tunnels under the coupling effect of earthquake and marine abrasion，the research includes: seismic responses of the main tunnel and cross structures, interaction mechanics mechanism of the double linings, earthquake damage mechanism and variation pattern of seismic performance along with the service age of shield tunnel. It is expected to build an earthquake response analysis model of subsea shield tunnels in different service ages, to reveal the effect of the secondary lining on the seismic performance of the tunnel, to establish an evaluation method on life-cycle seismic performance of subsea shield tunnels and to propose engineering measures and parameters to reduce and resist seismic damage of main tunnel and cross structures, which can offer theory and technology help for life-cycle healthy service in a lot of subsea shield tunnels those will be built in the future.

我国连接各大沿海经济区海底隧道工程的规划、建设正渐入高潮，琼州海峡通道、渤海海峡通道等世界级海底隧道的建设已然临近，而我国沿海正处于世界上两大地震带之一的环太平洋地震带上，特别是渤海海峡、台湾海峡、琼州海峡均处于强震活跃区，且近期地震活动频繁，这促使我们更加关注我国海底隧道工程的地震安全性。本项研究结合近海工程场地的地震动特征、海洋地质体、海蚀和盾构隧道的特点，针对海底盾构隧道全寿命抗震性能，研究地震与海蚀耦合作用下，隧道主体与交叉结构的地震响应特征、盾构隧道双层衬砌相互作用力学机制、盾构隧道地震损伤机理及隧道抗震性能随服役龄期的变化规律等关键科学问题，以期建立海底盾构隧道不同服役龄期地震响应分析模型，探明二次衬砌对隧道抗震性能的影响，构建海底盾构隧道全寿命抗震性能评价方法，提出盾构隧道与交叉结构的抗减震措施及关键设计参数，为今后大量海底盾构隧道全寿命周期的健康服役提供理论和技术支撑。

本项目基于海底盾构隧道特点，结合理论分析、数值模拟、室内试验以及振动台模型试验等手段，开展海底盾构隧道全寿命抗震性能研究。通过反应位移法建立海底盾构隧道单/双层衬砌横向分析模型，对比分析单、双层衬砌在不同水平地震作用下隧道内力的分布情况和变形规律,计算表明管片变形、弯矩、轴力呈反对称分布在结构两侧，相同地震动水平时双层衬砌地震附加总内力值高于单层衬砌；建立复合式/叠合式双层衬砌三维实体数值模型，开展地震作用下管片结构与二次衬砌内力及位移的分布特征分析，相同工况下，复合式衬砌管片的轴力、弯矩和二衬的弯矩均大于叠合式衬砌，复合式二衬的轴力小于叠合式二衬轴力；根据相似理论开展单、双层衬砌模型地震响应振动台试验，研究地震作用下单、双层衬砌盾构隧道跨越软硬突变地层的纵向动力响应特征，结果显示：软硬突变地层加速度响应频谱表现出与均匀地层显著不同的“双峰值”现象，管片纵向应变峰值包络线出现明显的“三峰值”，结构应变受地层影响的区域分布于地层交界面两侧2.5-3.5倍隧道直径范围；建立海底盾构隧道不同服役龄期地震响应分析模型，导入不同荷载水平下，随着氯离子侵蚀时间增长隧道结构劣化的本构模型，采用动力时程法分析隧道结构劣化抗震性能，以隧道直径变形率作为圆形盾构隧道的性能量化指标，提出了适用于圆形盾构隧道各性能水平的量化指标；开展隔震材料室内试验，沥青系隔震层能够有效降低衬砌拉、压应力及变形量，隔震层厚度分别为5cm、15cm及30cm时，对应减震率为46.3%、50.4%和58.2%；采用数值模拟及振动台试验，对海底盾构隧道交叉结构地震动力响应特性进行研究，采用刚性连接时，主隧道纵向受影响范围约为3倍横通道宽度，柔性连接可降低结构各处的应变和内力，降低影响范围至1.5-2倍。研究成果可为海底盾构隧道的设计和施工提供重要参考，为今后大量海底盾构隧道全寿命周期的健康服役提供理论和技术支撑。