基于锚喷-加筋喷混凝土拱肋技术的海底隧道软弱带围岩加固机制研究

There are great challenges for the construction of a subsea tunnel driven through weakness zones , and the combination of fiber reinforced shotcrete (Sfr), systematic bolting (B) and reinforced ribs of sprayed concrete (RRS), has been verified as the most cost-effective composite support system for reinforcing such unfavorable rock masses，which is used in several Norwegian subsea tunnels. However, because the composite supporting scheme mainly is designed according to the Q-chart，which is probablely too conservative or too insufficient in practice. .To this end, relying on some Norwegian Finnfast subsea tunnels, the performance of weakness zones is studied through different testing means, and the constitutive law of surrounding rock is introduced to the numerical simulation method, the collaborative working mechanism and common response between surrounding rock masses and different composite support methods are simulated. On this basis, the physical model tests are carried out to study the interaction mechanism and common response for rock masses and composite supports. Test results and simulation results are compared, the constitutive model and the simulation method are checked, and their further validation and improvement are done by the in situ monitoring data in Norway. Finally, the simulation method established is used to study the failure mechanism of surrounding rock masses in weakness zone and their reinforcement's technology, the design of the composite supports are optimized, and the Q-chart is improved. .The research results of this project are to provide a theoretical supports for the better application of the composite support in subsea tunnels in China, and thus have great theoretical and practical significance in engineering.

穿越软弱带给海底隧道建设带来巨大挑战。以锚喷（Sfr-B）和加筋喷混凝土拱肋（RRS）为组元的复合支护结构是当前加固该类围岩性价比最高的支护手段，在挪威多条海底隧道成功应用，但目前基于Q系统支护设计诺谟图设计的复合支护方案可能过于保守或偏不安全。本项目以挪威Finnfast和Fr?ya两条海底隧道为依托，通过试验研究软弱带围岩的性状，建立围岩本构模型；编制程序模块并嵌入数值软件，对围岩与复合支护结构的协同工作机制与响应进行仿真分析；开展围岩与复合支护相互作用及协同响应的物理模型试验，将试验成果与仿真结果进行对比，考证仿真方法，并进一步利用现场监测数据进行检验与完善；基于该仿真方法深入研究不同复合支护结构的加固机制与整体加固效应，优化复合支护的结构型式和支护时机，扩展Q系统支护设计诺谟图。本项目的研究成果为在我国海底隧道更好地应用该复合支护提供理论支持，具有重大的理论意义与应用价值。

穿越软弱带不仅给海底隧道建设带来巨大挑战，还使支护成本急剧增加，因而采用安全、经济的支护手段保障软弱带围岩稳定一直是海底隧道建设中的热点和难点问题。高性能湿喷纤维喷混凝土、系统锚杆、加筋喷混凝土拱肋等为组元的锚喷-加筋喷混凝土拱肋复合支护结构，在大量的海底工程实践中被证明是加固软弱带围岩（Q值< 1）性价比很高的支护手段。然而，目前该复合支护体系与软弱带围岩的协同工作机制尚不太清楚，锚喷支护结构的尺寸与布置主要根据Q系统支护设计诺谟图这一半经验法确定，导致工程实践中的复合支护结构可能偏保守或不安全，影响了其作为永久衬砌在我国海底隧道软弱带围岩加固处治中的应用。.本项目首先对挪威几座在役海底隧道软弱带围岩进行现场踏勘、取样与监测，通过试验手段研究了不同组份软弱带混合物的膨胀特征与渗流特性，揭示了软弱带混合物膨胀力范围以及黏粒含量对软弱带混合物土水特性的影响规律。然后，基于流变理论建立了软弱带围岩黏弹塑性本构模型，并结合海底围岩变形监测数据，基于BP神经网络法反演了围岩流变参数。接着，将建立的流变本构模型程序化并嵌入数值软件，对围岩与复合支护结构的协同工作机制与响应进行了仿真分析，并与围岩现场监测数据进行对比，揭示了海底软弱带围岩长期变形规律及复合支护力学响应。最后，系统研究不同结构型式复合支护的联合承载机制与整体加固效果，优化了该复合支护的结构型式和支护时机，为Q系统支护设计诺谟图改进提供了技术支持。该研究成果对海底隧道建设、海底矿物开采等海底空间开发实践有重要的科学意义和工程应用价值。