海底盾构隧道岩土工程设计理论与对策

Shield excavation is the main construction method for subsea tunnels in soft soils and soft rock. The mechanism of the earth and water pressure, seepage force on the shield tunnel lining and face, settlement characteristics, waterproof mechanism and seismic performance is not clear for subsea tunnel under the combined dynamic loading of high water head, wave loading, traffic loading and earthquake. Corresponding geotechnical engineering design theory is urgently needed for its safe construction and stable long-term operation.. This project aims to carry out key scientific issues in the design of subsea shield tunnel. Based on the numerical simulation, laboratory test and theoretical analysis, this project intends to propose a method to calculate the support pressure on the cutting face and the earth and water pressure on the lining structure. Considering the weakening effect of soil properties under combined wave and traffic loading, the calculation of long term longitudinal settlement will be put forward. The deformation mechanism of shield tunnel segment, the waterproofing failure and the soil erosion mechanism will be proclaimed. The seismic performance of long tunnel has the character of multi-site earthquake inputs; therefore the water-soil-tunnel interaction will be studied from multi-phase, multi-field coupling analysis and in the end seismic analysis software will be developed. The purpose of this research is to establish theory framework for the geotechnical design of subsea shield tunnel, based upon which the engineering countermeasures for safety operation could be proposed. This project will provide a theoretical basis and technical support for the study of sea-crossing transportation infrastructure. This prospective and scientific research is very crucial and urgent in order to protect the security of national major transportation infrastructures.

盾构法是土质或软岩地基中海底隧道建设的主要工程方法。海底盾构隧道在高水头和长期波浪、交通荷载及地震荷载等复杂动荷载作用下的隧道受力变形、沉降特性、防水机理和抗震性能尚不清楚，其建设和长期运营急需相关岩土工程设计理论支撑。. 本项目拟针对海底盾构隧道设计中关键科学问题开展基础性研究，提出波浪、强风暴潮循环作用下海底盾构隧道掘进面的支护压力和衬砌外水土压力计算方法；基于海底隧道周围土体在复杂荷载下的弱化特性和渗透性变化，建立隧道基础纵向沉降计算理论；揭示纵向不均匀沉降作用下水下盾构隧道管片接缝的受力变形机制、防水失效机理和水土流失机制；考虑长线隧道结构抗震多点不同输入的特点，研制多相多场耦合和水-土-隧道结构相互作用的抗震分析软件。本项目研究旨在建立海底盾构隧道岩土工程设计理论，为海底盾构隧道研究提供理论依据和技术支持，为保障国家相关重大交通基础设施的安全提供科学化和前瞻性的理论基础。

盾构法是土质或软岩地基中海底隧道建设的主要工程方法。海底盾构隧道在高水头和长期波浪、交通荷载及地震荷载等复杂动荷载作用下的隧道受力变形、沉降特性、防水机理和抗震性能尚不清楚，其建设和长期运营急需相关岩土工程设计理论支撑。. 本项目针对海底盾构隧道设计中关键科学问题开展基础性研究。从研究潮波作用下海底盾构隧道周围与开挖面前方的孔压响应规律出发，分析了隧道渗透性对隧道周围海床内渗流场的影响，分析了不同潮波要素（波高、潮差、周期、水深）与土层参数对海底盾构隧道附近孔压响应、隧道涌水量、隧道掘进面极限支护压力的影响。通过将潮波循环作用抽象成理论模型中的力学要素，为海底盾构隧道掘进面的支护压力和衬砌外水土压力计算提供了思路。. 基于海底隧道周围土体在复杂荷载下的弱化特性和渗透性变化，研究了海底高水头和海水环境对土体力学特性和渗透特性的影响，提出了交通荷载下考虑土体各向异性及非共轴特性的海底隧道沉降计算理论；研究了长期不均匀沉降作用下水下盾构隧道管片接缝的受力和变形机制，揭示了隧道接缝处弹性密封垫的防水失效机制，提出了盾构隧道长期运营中弹性密封垫的防水性能的评价体系，并提出工程对策。构建了非局部-Biot理论模型，得到地震波作用下海底深埋圆形隧道和浅埋圆形隧道的解析解。基于混合物理论，建立了准饱和土中的动力波动方程，导出了四种地震体波的波速及衰减的解析表达式。考虑到实际海床表面的不规则性，通过波函数展开法，求解了不规则海床表面的地震响应问题，获得了解析解。建立了P 波、S 波耦合作用下隧道地震响应模型，获得了随带衬砌和周边土体的应力和位移场的解析表达式。. 本项目研究为海底盾构隧道研究提供理论依据和技术支持，为保障国家相关重大交通基础设施的安全提供科学化和前瞻性的理论基础。